diff --git a/NEWS b/NEWS
index d2300393..1f2add46 100644
--- a/NEWS
+++ b/NEWS
@@ -1,2289 +1,2295 @@
 0.20.28	UNRELEASED
 
+ * Fix hook test on Mac OSX / Linux when dulwich is
+   not installed system-wide. (Jelmer Vernooij, #919)
+
+ * Cope with gecos being unset.
+   (Jelmer Vernooij, #917)
+
 0.20.27	2022-01-04
 
  * Allow adding files to repository in pre-commit hook.
    (Jelmer Vernooij, #916)
 
  * Raise SubmoduleEncountered in ``tree_lookup_path``.
    (Jelmer Vernooij)
 
 0.20.26	2021-10-29
 
  * Support os.PathLike arguments to Repo.stage().
    (Jan Wiśniewski, #907)
 
  * Drop support for Python 3.5.  (Jelmer Vernooij)
 
  * Add ``dulwich.porcelain._reset_file``.
    (Ded_Secer)
 
  * Add ``Repo.unstage``. (Ded_Secer)
 
 0.20.25	2021-08-23
 
  * Fix ``dulwich`` script when installed via setup.py.
    (Dan Villiom Podlaski Christiansen)
 
  * Make default file mask consistent
    with Git. (Dan Villiom Podlaski Christiansen, #884)
 
 0.20.24	2021-07-18
 
  * config: disregard UTF-8 BOM when reading file.
    (Dan Villiom Podlaski Christiansen)
 
  * Skip lines with spaces only in .gitignore. (Andrey Torsunov, #878)
 
  * Add a separate HTTPProxyUnauthorized exception for 407 errors.
    (Jelmer Vernooij, #822)
 
  * Split out a AbstractHTTPGitClient class.
    (Jelmer Vernooij)
 
 0.20.23	2021-05-24
 
  * Fix installation of GPG during package publishing.
    (Ruslan Kuprieiev)
 
 0.20.22	2021-05-24
 
  * Prevent removal of refs directory when the last ref is
    deleted. (Jelmer Vernooij)
 
  * Fix filename: MERGE_HEADS => MERGE_HEAD.
    (Jelmer Vernooij, #861)
 
  * For ignored directories, porcelain.add and porcelain.status now only return
    the path to directory itself in the list of ignored paths. Previously, paths
    for all files within the directory would also be included in the list.
    (Peter Rowlands, #853)
 
  * Provide depth argument to ``determine_wants``.
    (Peter Rowlands)
 
  * Various tag signature handling improvements.
    (Daniel Murphy)
 
  * Add separate Tag.verify().  (Peter Rowlands)
 
  * Add support for version 3 index files. (Jelmer Vernooij)
 
  * Fix autocrlf=input handling. (Peter Rowlands, Boris Feld)
 
  * Attempt to find C Git global config on Windows.
    (Peter Rowlands)
 
  API CHANGES
 
  * The APIs for writing and reading individual index entries have changed
    to handle lists of (name, entry) tuples rather than tuples.
 
 0.20.21	2021-03-20
 
  * Add basic support for a GcsObjectStore that stores
    pack files in gcs. (Jelmer Vernooij)
 
  * In porcelain.push, default to local active branch.
    (Jelmer Vernooij, #846)
 
  * Support fetching symrefs.
    (Jelmer Vernooij, #485, #847)
 
  * Add aarch64 wheel building.
    (odidev, Jelmer Vernooij)
 
 0.20.20	2021-03-03
 
  * Implement ``Stash.drop``. (Peter Rowlands)
 
  * Support untracked symlinks to paths outside the
    repository. (Peter Rowlands, #842)
 
 0.20.19	2021-02-11
 
  * Fix handling of negative matches in nested gitignores.
    (Corentin Hembise, #836)
 
 0.20.18	2021-02-04
 
  * Fix formatting in setup.py. (Jelmer Vernooij)
 
  * Add release configuration. (Jelmer Vernooij)
 
 0.20.17	2021-02-04
 
  * credentials: ignore end-of-line character. (Georges Racinet)
 
  * Fix failure in get_untracked_paths when the repository contains symlinks.
    (#830, #793, mattseddon)
 
  * docs: Clarify that Git objects are created on `git add`.
    (Utku Gultopu)
 
 0.20.16	2021-01-16
 
  * Add flag to only attempt to fetch ignored untracked files when specifically requested.
    (Matt Seddon)
 
 0.20.15	2020-12-23
 
  * Add some functions for parsing and writing bundles.
    (Jelmer Vernooij)
 
  * Add ``no_verify`` flag to ``porcelain.commit`` and ``Repo.do_commit``.
    (Peter Rowlands)
 
  * Remove dependency on external mock module.
    (Matěj Cepl, #820)
 
 0.20.14	2020-11-26
 
  * Fix some stash functions on Python 3. (Peter Rowlands)
 
  * Fix handling of relative paths in alternates files on Python 3.
    (Georges Racinet)
 
 0.20.13	2020-11-22
 
  * Add py.typed to allow type checking. (David Caro)
 
  * Add tests demonstrating a bug in the walker code.
    (Doug Hellman)
 
 0.20.11	2020-10-30
 
  * Fix wheels build on Linux. (Ruslan Kuprieiev)
 
  * Enable wheels build for Python 3.9 on Linux. (Jelmer Vernooij)
 
 0.20.8	2020-10-29
 
  * Build wheels on Mac OS X / Windows for Python 3.9.
    (Jelmer Vernooij)
 
 0.20.7	2020-10-29
 
  * Check core.repositoryformatversion. (Jelmer Vernooij, #803)
 
  * Fix ACK/NACK handling in archive command handling in dulwich.client.
    (DzmitrySudnik, #805)
 
 0.20.6	2020-08-29
 
  * Add a ``RefsContainer.watch`` interface.
    (Jelmer Vernooij, #751)
 
  * Fix pushing of new branches from porcelain.push.
    (Jelmer Vernooij, #788)
 
  * Honor shallows when pushing from a shallow clone.
    (Jelmer Vernooij, #794)
 
  * Fix porcelain.path_to_tree_path for Python 3.5.
    (Boris Feld, #777)
 
  * Add support for honor proxy environment variables for HTTP.
    (Aurélien Campéas, #797)
 
 0.20.5	2020-06-22
 
  * Print a clearer exception when setup.py is executed on Python < 3.5.
    (Jelmer Vernooij, #783)
 
  * Send an empty pack to clients if they requested objects, even if they
    already have those objects. Thanks to Martijn Pieters for
    the detailed bug report. (Jelmer Vernooij, #781)
 
  * porcelain.pull: Don't ask for objects that we already have.
    (Jelmer Vernooij, #782)
 
  * Add LCA implementation. (Kevin Hendricks)
 
  * Add functionality for finding the merge base. (Kevin Hendricks)
 
  * Check for diverged branches during push.
    (Jelmer Vernooij, #494)
 
  * Check for fast-forward during pull. (Jelmer Vernooij, #666)
 
  * Return a SendPackResult object from
    GitClient.send_pack(). (Jelmer Vernooij)
 
  * ``GitClient.send_pack`` now sets the ``ref_status`` attribute
    on its return value to a dictionary mapping ref names
    to error messages. Previously, it raised UpdateRefsError
    if any of the refs failed to update.
    (Jelmer Vernooij, #780)
 
  * Add a ``porcelain.Error`` object that most errors in porcelain
    derive from. (Jelmer Vernooij)
 
  * Fix argument parsing in dulwich command-line app.
    (Jelmer Vernooij, #784)
 
 0.20.3	2020-06-14
 
  * Add support for remembering remote refs after push/pull.
    (Jelmer Vernooij, #752)
 
  * Support passing tree and output encoding to
    dulwich.patch.unified_diff. (Jelmer Vernooij, #763)
 
  * Fix pushing of new refs over HTTP(S) when there are
    no new objects to be sent.
    (Jelmer Vernooij, #739)
 
  * Raise new error HTTPUnauthorized when the server sends
    back a 401. The client can then retry with credentials.
    (Jelmer Vernooij, #691)
 
  * Move the guts of bin/dulwich to dulwich.cli, so it is easier to
    test or import. (Jelmer Vernooij)
 
  * Install dulwich script from entry_points when setuptools is available,
    making it slightly easier to use on Windows. (Jelmer Vernooij, #540)
 
  * Set python_requires>=3.5 in setup.py. (Manuel Jacob)
 
 0.20.2	2020-06-01
 
  * Brown bag release to fix uploads of Windows wheels.
 
 0.20.1	2020-06-01
 
  * Publish binary wheels for: Windows, Linux, Mac OS X.
    (Jelmer Vernooij, #711, #710, #629)
 
 0.20.0	2020-06-01
 
  * Drop support for Python 2. (Jelmer Vernooij)
 
  * Only return files from the loose store that look like git objects.
    (Nicolas Dandrimont)
 
  * Ignore agent= capability if sent by client.
    (Jelmer Vernooij)
 
  * Don't break when encountering block devices.
    (Jelmer Vernooij)
 
  * Decode URL paths in HttpGitClient using utf-8 rather than file system
    encoding. (Manuel Jacob)
 
  * Fix pushing from a shallow clone.
    (Brecht Machiels, #705)
 
 0.19.16	2020-04-17
 
  * Don't send "deepen None" to server if graph walker
    supports shallow. (Jelmer Vernooij, #747)
 
  * Support tweaking the compression level for
    loose objects through the "core.looseCompression" and
    "core.compression" settings. (Jelmer Vernooij)
 
  * Support tweaking the compression level for
    pack objects through the "core.packCompression" and
    "core.compression" settings. (Jelmer Vernooij)
 
  * Add a "dulwich.contrib.diffstat" module.
    (Kevin Hendricks)
 
 0.19.15	2020-01-26
 
  * Properly handle files that are just executable for the
    current user. (Jelmer Vernooij, #734)
 
  * Fix handling of stored encoding in
    ``dulwich.porcelain.get_object_by_path`` on Python 3.
    (Jelmer Vernooij)
 
  * Support the include_trees and rename_detector arguments
    at the same time when diffing trees.
    (Jelmer Vernooij)
 
 0.19.14	2019-11-30
 
  * Strip superfluous <> around email. (monnerat)
 
  * Stop checking for ref validity client-side. Users can
    still call check_wants manually. (Jelmer Vernooij)
 
  * Switch over to Google-style docstrings.
    (Jelmer Vernooij)
 
  * Add a ``dulwich.porcelain.active_branch`` function.
    (Jelmer Vernooij)
 
  * Cleanup new directory if clone fails. (Jelmer Vernooij, #733)
 
  * Expand "~" in global exclude path. (Jelmer Vernooij)
 
 0.19.13	2019-08-19
 
  BUG FIXES
 
  * Avoid ``PermissionError``, since it is Python3-specific.
    (Jelmer Vernooij)
 
  * Fix regression that added a dependency on C git for the
    test suite. (Jelmer Vernooij, #720)
 
  * Fix compatibility with Python 3.8 - mostly deprecation warnings.
    (Jelmer Vernooij)
 
 0.19.12	2019-08-13
 
  BUG FIXES
 
  * Update directory detection for `get_unstaged_changes` for Python 3.
    (Boris Feld, #684)
 
  * Add a basic ``porcelain.clean``. (Lane Barlow, #398)
 
  * Fix output format of ``porcelain.diff`` to match that of
    C Git. (Boris Feld)
 
  * Return a 404 not found error when repository is not found.
 
  * Mark ``.git`` directories as hidden on Windows.
    (Martin Packman, #585)
 
  * Implement ``RefsContainer.__iter__``
    (Jelmer Vernooij, #717)
 
  * Don't trust modes if they can't be modified after a file has been created.
    (Jelmer Vernooij, #719)
 
 0.19.11	2019-02-07
 
  IMPROVEMENTS
 
  * Use fullname from gecos field, if available.
    (Jelmer Vernooij)
 
  * Support ``GIT_AUTHOR_NAME`` / ``GIT_AUTHOR_EMAIL``.
    (Jelmer Vernooij)
 
  * Add support for short ids in parse_commit. (Jelmer Vernooij)
 
  * Add support for ``prune`` and ``prune_tags`` arguments
    to ``porcelain.fetch``. (Jelmer Vernooij, #681)
 
  BUG FIXES
 
   * Fix handling of race conditions when new packs appear.
     (Jelmer Vernooij)
 
 0.19.10	2018-01-15
 
  IMPROVEMENTS
 
  * Add `dulwich.porcelain.write_tree`.
    (Jelmer Vernooij)
 
  * Support reading ``MERGE_HEADS`` in ``Repo.do_commit``.
    (Jelmer Vernooij)
 
  * Import from ``collections.abc`` rather than ``collections`` where
    applicable. Required for 3.8 compatibility.
    (Jelmer Vernooij)
 
  * Support plain strings as refspec arguments to
    ``dulwich.porcelain.push``. (Jelmer Vernooij)
 
  * Add support for creating signed tags.
    (Jelmer Vernooij, #542)
 
  BUG FIXES
 
  *  Handle invalid ref that pretends to be a sub-folder under a valid ref.
     (KS Chan)
 
 0.19.9	2018-11-17
 
  BUG FIXES
 
  * Avoid fetching ghosts in ``Repo.fetch``.
    (Jelmer Vernooij)
 
  * Preserve port and username in parsed HTTP URLs.
    (Jelmer Vernooij)
 
  * Add basic server side implementation of ``git-upload-archive``.
    (Jelmer Vernooij)
 
 0.19.8	2018-11-06
 
  * Fix encoding when reading README file in setup.py.
    (egor <egor@sourced.tech>, #668)
 
 0.19.7	2018-11-05
 
  CHANGES
 
   * Drop support for Python 3 < 3.4. This is because
     pkg_resources (which get used by setuptools and mock)
     no longer supports 3.3 and earlier. (Jelmer Vernooij)
 
  IMPROVEMENTS
 
   * Support ``depth`` argument to ``GitClient.fetch_pack`` and support
     fetching and updating shallow metadata. (Jelmer Vernooij, #240)
 
  BUG FIXES
 
   * Don't write to stdout and stderr when they are not available
     (such as is the case for pythonw). (Sylvia van Os, #652)
 
   * Fix compatibility with newer versions of git, which expect CONTENT_LENGTH
     to be set to 0 for empty body requests. (Jelmer Vernooij, #657)
 
   * Raise an exception client-side when a caller tries to request
     SHAs that are not directly referenced the servers' refs.
     (Jelmer Vernooij)
 
   * Raise more informative errors when unable to connect to repository
     over SSH or subprocess. (Jelmer Vernooij)
 
   * Handle commit identity fields with multiple ">" characters.
     (Nicolas Dandrimont)
 
  IMPROVEMENTS
 
   * ``dulwich.porcelain.get_object_by_path`` method for easily
     accessing a path in another tree. (Jelmer Vernooij)
 
   * Support the ``i18n.commitEncoding`` setting in config.
     (Jelmer Vernooij)
 
 0.19.6	2018-08-11
 
  BUG FIXES
 
   * Fix support for custom transport arguments in ``dulwich.porcelain.clone``.
     (Semyon Slepov)
 
   * Fix compatibility with Python 3.8 (Jelmer Vernooij, Daniel M. Capella)
 
   * Fix some corner cases in ``path_to_tree_path``. (Romain Keramitas)
 
   * Support paths as bytestrings in various places in ``dulwich.index``
     (Jelmer Vernooij)
 
   * Avoid setup.cfg for now, since it seems to break pypi metadata.
     (Jelmer Vernooij, #658)
 
 0.19.5	2018-07-08
 
  IMPROVEMENTS
 
   * Add ``porcelain.describe``. (Sylvia van Os)
 
  BUG FIXES
 
   * Fix regression in ``dulwich.porcelain.clone`` that prevented cloning
     of remote repositories. (Jelmer Vernooij, #639)
 
   * Don't leave around empty parent directories for removed refs.
     (Damien Tournoud, #640)
 
 0.19.4	2018-06-24
 
  IMPROVEMENTS
 
   * Add ``porcelain.ls_files``. (Jelmer Vernooij)
 
   * Add ``Index.items``. (Jelmer Vernooij)
 
  BUG FIXES
 
   * Avoid unicode characters (e.g. the digraph ij in my surname) in setup.cfg,
     since setuptools doesn't deal well with them. See
     https://github.com/pypa/setuptools/issues/1062. (Jelmer Vernooij, #637)
 
 0.19.3	2018-06-17
 
  IMPROVEMENTS
 
   * Add really basic `dulwich.porcelain.fsck` implementation.
     (Jelmer Vernooij)
 
   * When the `DULWICH_PDB` environment variable is set, make
     SIGQUIT open pdb in the 'dulwich' command.
 
   * Add `checkout` argument to `Repo.clone`.
     (Jelmer Vernooij, #503)
 
   * Add `Repo.get_shallow` method. (Jelmer Vernooij)
 
   * Add basic `dulwich.stash` module. (Jelmer Vernooij)
 
   * Support a `prefix` argument to `dulwich.archive.tar_stream`.
     (Jelmer Vernooij)
 
  BUG FIXES
 
   * Fix handling of encoding for tags. (Jelmer Vernooij, #608)
 
   * Fix tutorial tests on Python 3. (Jelmer Vernooij, #573)
 
   * Fix remote refs created by `porcelain.fetch`. (Daniel Andersson, #623)
 
   * More robust pack creation on Windows. (Daniel Andersson)
 
   * Fix recursive option for `porcelain.ls_tree`. (Romain Keramitas)
 
  TESTS
 
   * Some improvements to paramiko tests. (Filipp Frizzy)
 
 0.19.2	2018-04-07
 
  BUG FIXES
 
   * Fix deprecated Index.iterblobs method.
     (Jelmer Vernooij)
 
 0.19.1	2018-04-05
 
  IMPROVEMENTS
 
   * Add 'dulwich.mailmap' file for reading mailmap files.
     (Jelmer Vernooij)
 
   * Dulwich no longer depends on urllib3[secure]. Instead,
     "dulwich[https]" can be used to pull in the necessary
     dependencies for HTTPS support. (Jelmer Vernooij, #616)
 
   * Support the `http.sslVerify` and `http.sslCAInfo`
     configuration options. (Jelmer Vernooij)
 
   * Factor out `dulwich.client.parse_rsync_url` function.
     (Jelmer Vernooij)
 
   * Fix repeat HTTP requests using the same smart HTTP client.
     (Jelmer Vernooij)
 
   * New 'client.PLinkSSHVendor' for creating connections using PuTTY's plink.exe.
     (Adam Bradley, Filipp Frizzy)
 
   * Only pass in `key_filename` and `password` to SSHVendor
     implementations if those parameters are set.
     (This helps with older SSHVendor implementations)
     (Jelmer Vernooij)
 
  API CHANGES
 
   * Index.iterblobs has been renamed to Index.iterobjects.
     (Jelmer Vernooij)
 
 0.19.0	2018-03-10
 
  BUG FIXES
 
   * Make `dulwich.archive` set the gzip header file modification time so that
     archives created from the same Git tree are always identical.
     (#577, Jonas Haag)
 
   * Allow comment characters (#, ;) within configuration file strings
     (Daniel Andersson, #579)
 
   * Raise exception when passing in invalid author/committer values
     to Repo.do_commit(). (Jelmer Vernooij, #602)
 
  IMPROVEMENTS
 
   * Add a fastimport ``extra``. (Jelmer Vernooij)
 
   * Start writing reflog entries. (Jelmer Vernooij)
 
   * Add ability to use password and keyfile ssh options with SSHVendor. (Filipp Kucheryavy)
 
   * Add ``change_type_same`` flag to ``tree_changes``.
     (Jelmer Vernooij)
 
  API CHANGES
 
   * ``GitClient.send_pack`` now accepts a ``generate_pack_data``
     rather than a ``generate_pack_contents`` function for
     performance reasons. (Jelmer Vernooij)
 
   * Dulwich now uses urllib3 internally for HTTP requests.
     The `opener` argument to `dulwich.client.HttpGitClient` that took a
     `urllib2` opener instance has been replaced by a `pool_manager` argument
     that takes a `urllib3` pool manager instance.
     (Daniel Andersson)
 
 0.18.6	2017-11-11
 
  BUG FIXES
 
   * Fix handling of empty repositories in ``porcelain.clone``.
     (#570, Jelmer Vernooij)
 
   * Raise an error when attempting to add paths that are not under the
     repository. (Jelmer Vernooij)
 
   * Fix error message for missing trailing ]. (Daniel Andersson)
 
   * Raise EmptyFileException when corruption (in the form of an empty
     file) is detected. (Antoine R. Dumont, #582)
 
   IMPROVEMENTS
 
   * Enforce date field parsing consistency. This also add checks on
     those date fields for potential overflow.
     (Antoine R. Dumont, #567)
 
 0.18.5	2017-10-29
 
  BUG FIXES
 
   * Fix cwd for hooks. (Fabian Grünbichler)
 
   * Fix setting of origin in config when non-standard origin is passed into
     ``Repo.clone``. (Kenneth Lareau, #565)
 
   * Prevent setting SSH arguments from SSH URLs when using SSH through a
     subprocess. Note that Dulwich doesn't support cloning submodules.
     (CVE-2017-16228) (Jelmer Vernooij)
 
  IMPROVEMENTS
 
   * Silently ignored directories in ``Repo.stage``.
     (Jelmer Vernooij, #564)
 
  API CHANGES
 
   * GitFile now raises ``FileLocked`` when encountering a lock
     rather than OSError(EEXIST). (Jelmer Vernooij)
 
 0.18.4	2017-10-01
 
  BUG FIXES
 
   * Make default User-Agent start with "git/" because GitHub won't response to
     HTTP smart server requests otherwise (and reply with a 404).
     (Jelmer vernooij, #562)
 
 0.18.3	2017-09-03
 
  BUG FIXES
 
   * Read config during porcelain operations that involve remotes.
     (Jelmer Vernooij, #545)
 
   * Fix headers of empty chunks in unified diffs. (Taras Postument, #543)
 
   * Properly follow redirects over HTTP. (Jelmer Vernooij, #117)
 
  IMPROVEMENTS
 
   * Add ``dulwich.porcelain.update_head``. (Jelmer Vernooij, #439)
 
   * ``GitClient.fetch_pack`` now returns symrefs.
     (Jelmer Vernooij, #485)
 
   * The server now supports providing symrefs.
     (Jelmer Vernooij, #485)
 
   * Add ``dulwich.object_store.commit_tree_changes`` to incrementally
     commit changes to a tree structure. (Jelmer Vernooij)
 
   * Add basic ``PackBasedObjectStore.repack`` method.
     (Jelmer Vernooij, Earl Chew, #296, #549, #552)
 
 0.18.2	2017-08-01
 
  TEST FIXES
 
   * Use constant timestamp so tests pass in all timezones, not just BST.
     (Jelmer Vernooij)
 
 0.18.1	2017-07-31
 
  BUG FIXES
 
   * Fix syntax error in dulwich.contrib.test_swift_smoke.
     (Jelmer Vernooij)
 
 0.18.0	2017-07-31
 
  BUG FIXES
 
   * Fix remaining tests on Windows. (Jelmer Vernooij, #493)
 
   * Fix build of C extensions with Python 3 on Windows.
     (Jelmer Vernooij)
 
   * Pass 'mkdir' argument onto Repo.init_bare in Repo.clone.
     (Jelmer Vernooij, #504)
 
   * In ``dulwich.porcelain.add``, if no files are specified,
     add from current working directory rather than repository root.
     (Jelmer Vernooij, #521)
 
   * Properly deal with submodules in 'porcelain.status'.
     (Jelmer Vernooij, #517)
 
   * ``dulwich.porcelain.remove`` now actually removes files from
     disk, not just from the index. (Jelmer Vernooij, #488)
 
   * Fix handling of "reset" command with markers and without
     "from". (Antoine Pietri)
 
   * Fix handling of "merge" command with markers. (Antoine Pietri)
 
   * Support treeish argument to porcelain.reset(), rather than
     requiring a ref/commit id. (Jelmer Vernooij)
 
   * Handle race condition when mtime doesn't change between writes/reads.
     (Jelmer Vernooij, #541)
 
   * Fix ``dulwich.porcelain.show`` on commits with Python 3.
     (Jelmer Vernooij, #532)
 
  IMPROVEMENTS
 
   * Add basic support for reading ignore files in ``dulwich.ignore``.
     ``dulwich.porcelain.add`` and ``dulwich.porcelain.status`` now honor
     ignores. (Jelmer Vernooij, Segev Finer, #524, #526)
 
   * New ``dulwich.porcelain.check_ignore`` command.
     (Jelmer Vernooij)
 
   * ``dulwich.porcelain.status`` now supports a ``ignored`` argument.
     (Jelmer Vernooij)
 
  DOCUMENTATION
 
   * Clarified docstrings for Client.{send_pack,fetch_pack} implementations.
     (Jelmer Vernooij, #523)
 
 0.17.3	2017-03-20
 
  PLATFORM SUPPORT
 
   * List Python 3.3 as supported. (Jelmer Vernooij, #513)
 
  BUG FIXES
 
   * Fix compatibility with pypy 3. (Jelmer Vernooij)
 
 0.17.2	2017-03-19
 
  BUG FIXES
 
   * Add workaround for
     https://bitbucket.org/pypy/pypy/issues/2499/cpyext-pystring_asstring-doesnt-work,
     fixing Dulwich when used with C extensions on pypy < 5.6. (Victor Stinner)
 
   * Properly quote config values with a '#' character in them.
     (Jelmer Vernooij, #511)
 
 0.17.1	2017-03-01
 
  IMPROVEMENTS
 
   * Add basic 'dulwich pull' command. (Jelmer Vernooij)
 
  BUG FIXES
 
   * Cope with existing submodules during pull.
     (Jelmer Vernooij, #505)
 
 0.17.0	2017-03-01
 
  TEST FIXES
 
   * Skip test that requires sync to synchronize filesystems if os.sync is
     not available. (Koen Martens)
 
  IMPROVEMENTS
 
   * Implement MemoryRepo.{set_description,get_description}.
     (Jelmer Vernooij)
 
   * Raise exception in Repo.stage() when absolute paths are
     passed in. Allow passing in relative paths to
     porcelain.add().(Jelmer Vernooij)
 
  BUG FIXES
 
   * Handle multi-line quoted values in config files.
     (Jelmer Vernooij, #495)
 
   * Allow porcelain.clone of repository without HEAD.
     (Jelmer Vernooij, #501)
 
   * Support passing tag ids to Walker()'s include argument.
     (Jelmer Vernooij)
 
   * Don't strip trailing newlines from extra headers.
     (Nicolas Dandrimont)
 
   * Set bufsize=0 for subprocess interaction with SSH client.
     Fixes hangs on Python 3. (René Stern, #434)
 
   * Don't drop first slash for SSH paths, except for those
     starting with "~". (Jelmer Vernooij, René Stern, #463)
 
   * Properly log off after retrieving just refs.
     (Jelmer Vernooij)
 
 0.16.3	2016-01-14
 
  TEST FIXES
 
   * Remove racy check that relies on clock time changing between writes.
     (Jelmer Vernooij)
 
  IMPROVEMENTS
 
   * Add porcelain.remote_add. (Jelmer Vernooij)
 
 0.16.2	2016-01-14
 
  IMPROVEMENTS
 
   * Fixed failing test-cases on windows.
     (Koen Martens)
 
  API CHANGES
 
   * Repo is now a context manager, so that it can be easily
     closed using a ``with`` statement. (Søren Løvborg)
 
  TEST FIXES
 
   * Only run worktree list compat tests against git 2.7.0,
     when 'git worktree list' was introduced. (Jelmer Vernooij)
 
  BUG FIXES
 
   * Ignore filemode when building index when core.filemode
     is false.
     (Koen Martens)
 
   * Initialize core.filemode configuration setting by
     probing the filesystem for trustable permissions.
     (Koen Martens)
 
   * Fix ``porcelain.reset`` to respect the comittish argument.
     (Koen Martens)
 
   * Fix dulwich.porcelain.ls_remote() on Python 3.
     (#471, Jelmer Vernooij)
 
   * Allow both unicode and byte strings for host paths
     in dulwich.client. (#435, Jelmer Vernooij)
 
   * Add remote from porcelain.clone. (#466, Jelmer Vernooij)
 
   * Fix unquoting of credentials before passing to urllib2.
     (#475, Volodymyr Holovko)
 
   * Cope with submodules in `build_index_from_tree`.
     (#477, Jelmer Vernooij)
 
   * Handle deleted files in `get_unstaged_changes`.
     (#483, Doug Hellmann)
 
   * Don't overwrite files when they haven't changed in
     `build_file_from_blob`.
     (#479, Benoît HERVIER)
 
   * Check for existence of index file before opening pack.
     Fixes a race when new packs are being added.
     (#482, wme)
 
 0.16.1	2016-12-25
 
  BUG FIXES
 
   * Fix python3 compatibility for dulwich.contrib.release_robot.
     (Jelmer Vernooij)
 
 0.16.0	2016-12-24
 
  IMPROVEMENTS
 
   * Add support for worktrees. See `git-worktree(1)` and
     `gitrepository-layout(5)`. (Laurent Rineau)
 
   * Add support for `commondir` file in Git control
     directories. (Laurent Rineau)
 
   * Add support for passwords in HTTP URLs.
     (Jon Bain, Mika Mäenpää)
 
   * Add `release_robot` script to contrib,
     allowing easy finding of current version based on Git tags.
     (Mark Mikofski)
 
   * Add ``Blob.splitlines`` method.
     (Jelmer Vernooij)
 
  BUG FIXES
 
   * Fix handling of ``Commit.tree`` being set to an actual
     tree object rather than a tree id. (Jelmer Vernooij)
 
   * Return remote refs from LocalGitClient.fetch_pack(),
     consistent with the documentation for that method.
     (#461, Jelmer Vernooij)
 
   * Fix handling of unknown URL schemes in get_transport_and_path.
     (#465, Jelmer Vernooij)
 
 0.15.0	2016-10-09
 
  BUG FIXES
 
   * Allow missing trailing LF when reading service name from
     HTTP servers. (Jelmer Vernooij, Andrew Shadura, #442)
 
   * Fix dulwich.porcelain.pull() on Python3. (Jelmer Vernooij, #451)
 
   * Properly pull in tags during dulwich.porcelain.clone.
     (Jelmer Vernooij, #408)
 
  CHANGES
 
   * Changed license from "GNU General Public License, version 2.0 or later"
     to "Apache License, version 2.0 or later or GNU General Public License,
     version 2.0 or later". (#153)
 
  IMPROVEMENTS
 
   * Add ``dulwich.porcelain.ls_tree`` implementation. (Jelmer Vernooij)
 
 0.14.1	2016-07-05
 
  BUG FIXES
 
   * Fix regression removing untouched refs when pushing over SSH.
     (Jelmer Vernooij #441)
 
   * Skip Python3 tests for SWIFT contrib module, as it has not yet
     been ported.
 
 0.14.0	2016-07-03
 
  BUG FIXES
 
   * Fix ShaFile.id after modification of a copied ShaFile.
     (Félix Mattrat, Jelmer Vernooij)
 
   * Support removing refs from porcelain.push.
     (Jelmer Vernooij, #437)
 
   * Stop magic protocol ref `capabilities^{}` from leaking out
     to clients. (Jelmer Vernooij, #254)
 
  IMPROVEMENTS
 
   * Add `dulwich.config.parse_submodules` function.
 
   * Add `RefsContainer.follow` method. (#438)
 
 0.13.0	2016-04-24
 
  IMPROVEMENTS
 
   * Support `ssh://` URLs in get_transport_and_path_from_url().
     (Jelmer Vernooij, #402)
 
   * Support missing empty line after headers in Git commits and tags.
     (Nicolas Dandrimont, #413)
 
   * Fix `dulwich.porcelain.status` when used in empty trees.
     (Jelmer Vernooij, #415)
 
   * Return copies of objects in MemoryObjectStore rather than
     references, making the behaviour more consistent with that of
     DiskObjectStore. (Félix Mattrat, Jelmer Vernooij)
 
   * Fix ``dulwich.web`` on Python3. (#295, Jonas Haag)
 
  CHANGES
 
   * Drop support for Python 2.6.
 
   * Fix python3 client web support. (Jelmer Vernooij)
 
  BUG FIXES
 
   * Fix hang on Gzip decompression. (Jonas Haag)
 
   * Don't rely on working tell() and seek() methods
     on wsgi.input. (Jonas Haag)
 
   * Support fastexport/fastimport functionality on python3 with newer
     versions of fastimport (>= 0.9.5). (Jelmer Vernooij, Félix Mattrat)
 
 0.12.0	2015-12-13
 
  IMPROVEMENTS
 
   * Add a `dulwich.archive` module that can create tarballs.
     Based on code from Jonas Haag in klaus.
 
   * Add a `dulwich.reflog` module for reading and writing reflogs.
     (Jelmer Vernooij)
 
   * Fix handling of ambiguous refs in `parse_ref` to make
     it match the behaviour described in https://git-scm.com/docs/gitrevisions.
     (Chris Bunney)
 
   * Support Python3 in C modules. (Lele Gaifax)
 
  BUG FIXES
 
   * Simplify handling of SSH command invocation.
     Fixes quoting of paths. Thanks, Thomas Liebetraut. (#384)
 
   * Fix inconsistent handling of trailing slashes for DictRefsContainer. (#383)
 
   * Add hack to support thin packs duing fetch(), albeit while requiring the
     entire pack file to be loaded into memory. (jsbain)
 
  CHANGES
 
   * This will be the last release to support Python 2.6.
 
 0.11.2	2015-09-18
 
  IMPROVEMENTS
 
   * Add support for agent= capability. (Jelmer Vernooij, #298)
 
   * Add support for quiet capability. (Jelmer Vernooij)
 
  CHANGES
 
   * The ParamikoSSHVendor class has been moved to
   * dulwich.contrib.paramiko_vendor, as it's currently untested.
     (Jelmer Vernooij, #364)
 
 0.11.1	2015-09-13
 
  Fix-up release to exclude broken blame.py file.
 
 0.11.0	2015-09-13
 
  IMPROVEMENTS
 
   * Extended Python3 support to most of the codebase.
     (Gary van der Merwe, Jelmer Vernooij)
   * The `Repo` object has a new `close` method that can be called to close any
     open resources. (Gary van der Merwe)
   * Support 'git.bat' in SubprocessGitClient on Windows.
     (Stefan Zimmermann)
   * Advertise 'ofs-delta' capability in receive-pack server side
     capabilities. (Jelmer Vernooij)
   * Switched `default_local_git_client_cls` to `LocalGitClient`.
     (Gary van der Merwe)
   * Add `porcelain.ls_remote` and `GitClient.get_refs`.
     (Michael Edgar)
   * Add `Repo.discover` method. (B. M. Corser)
   * Add `dulwich.objectspec.parse_refspec`. (Jelmer Vernooij)
   * Add `porcelain.pack_objects` and `porcelain.repack`.
     (Jelmer Vernooij)
 
  BUG FIXES
 
   * Fix handling of 'done' in graph walker and implement the
     'no-done' capability. (Tommy Yu, #88)
 
   * Avoid recursion limit issues resolving deltas. (William Grant, #81)
 
   * Allow arguments in local client binary path overrides.
     (Jelmer Vernooij)
 
   * Fix handling of commands with arguments in paramiko SSH
     client. (Andreas Klöckner, Jelmer Vernooij, #363)
 
   * Fix parsing of quoted strings in configs. (Jelmer Vernooij, #305)
 
 0.10.1  2015-03-25
 
  BUG FIXES
 
   * Return `ApplyDeltaError` when encountering delta errors
     in both C extensions and native delta application code.
     (Jelmer Vernooij, #259)
 
 0.10.0	2015-03-22
 
  BUG FIXES
 
   * In dulwich.index.build_index_from_tree, by default
     refuse to create entries that start with .git/.
     (Jelmer Vernooij, CVE-2014-9706)
 
   * Fix running of testsuite when installed.
     (Jelmer Vernooij, #223)
 
   * Use a block cache in _find_content_rename_candidates(),
     improving performance. (Mike Williams)
 
   * Add support for ``core.protectNTFS`` setting.
     (Jelmer Vernooij)
 
   * Fix TypeError when fetching empty updates.
     (Hwee Miin Koh)
 
   * Resolve delta refs when pulling into a MemoryRepo.
     (Max Shawabkeh, #256)
 
   * Fix handling of tags of non-commits in missing object finder.
     (Augie Fackler, #211)
 
   * Explicitly disable mmap on plan9 where it doesn't work.
     (Jeff Sickel)
 
  IMPROVEMENTS
 
   * New public method `Repo.reset_index`. (Jelmer Vernooij)
 
   * Prevent duplicate parsing of loose files in objects
     directory when reading. Thanks to David Keijser for the
     report. (Jelmer Vernooij, #231)
 
 0.9.9	2015-03-20
 
  SECURITY BUG FIXES
 
   * Fix buffer overflow in C implementation of pack apply_delta().
     (CVE-2015-0838)
 
     Thanks to Ivan Fratric of the Google Security Team for
     reporting this issue.
     (Jelmer Vernooij)
 
 0.9.8	2014-11-30
 
  BUG FIXES
 
   * Various fixes to improve test suite running on Windows.
     (Gary van der Merwe)
 
   * Limit delta copy length to 64K in v2 pack files. (Robert Brown)
 
   * Strip newline from final ACKed SHA while fetching packs.
     (Michael Edgar)
 
   * Remove assignment to PyList_SIZE() that was causing segfaults on
     pypy. (Jelmer Vernooij, #196)
 
  IMPROVEMENTS
 
   * Add porcelain 'receive-pack' and 'upload-pack'. (Jelmer Vernooij)
 
   * Handle SIGINT signals in bin/dulwich. (Jelmer Vernooij)
 
   * Add 'status' support to bin/dulwich. (Jelmer Vernooij)
 
   * Add 'branch_create', 'branch_list', 'branch_delete' porcelain.
     (Jelmer Vernooij)
 
   * Add 'fetch' porcelain. (Jelmer Vernooij)
 
   * Add 'tag_delete' porcelain. (Jelmer Vernooij)
 
   * Add support for serializing/deserializing 'gpgsig' attributes in Commit.
     (Jelmer Vernooij)
 
  CHANGES
 
   * dul-web is now available as 'dulwich web-daemon'.
     (Jelmer Vernooij)
 
   * dulwich.porcelain.tag has been renamed to tag_create.
     dulwich.porcelain.list_tags has been renamed to tag_list.
     (Jelmer Vernooij)
 
  API CHANGES
 
   * Restore support for Python 2.6. (Jelmer Vernooij, Gary van der Merwe)
 
 
 0.9.7	2014-06-08
 
  BUG FIXES
 
   * Fix tests dependent on hash ordering. (Michael Edgar)
 
   * Support staging symbolic links in Repo.stage.
     (Robert Brown)
 
   * Ensure that all files object are closed when running the test suite.
     (Gary van der Merwe)
 
   * When writing OFS_DELTA pack entries, write correct offset.
     (Augie Fackler)
 
   * Fix handler of larger copy operations in packs. (Augie Fackler)
 
   * Various fixes to improve test suite running on Windows.
     (Gary van der Merwe)
 
   * Fix logic for extra adds of identical files in rename detector.
     (Robert Brown)
 
  IMPROVEMENTS
 
   * Add porcelain 'status'. (Ryan Faulkner)
 
   * Add porcelain 'daemon'. (Jelmer Vernooij)
 
   * Add `dulwich.greenthreads` module which provides support
     for concurrency of some object store operations.
     (Fabien Boucher)
 
   * Various changes to improve compatibility with Python 3.
     (Gary van der Merwe, Hannu Valtonen, michael-k)
 
   * Add OpenStack Swift backed repository implementation
     in dulwich.contrib. See README.swift for details. (Fabien Boucher)
 
 API CHANGES
 
   * An optional close function can be passed to the Protocol class. This will
     be called by its close method. (Gary van der Merwe)
 
   * All classes with close methods are now context managers, so that they can
     be easily closed using a `with` statement. (Gary van der Merwe)
 
   * Remove deprecated `num_objects` argument to `write_pack` methods.
     (Jelmer Vernooij)
 
  OTHER CHANGES
 
   * The 'dul-daemon' script has been removed. The same functionality
     is now available as 'dulwich daemon'. (Jelmer Vernooij)
 
 0.9.6	2014-04-23
 
  IMPROVEMENTS
 
   * Add support for recursive add in 'git add'.
     (Ryan Faulkner, Jelmer Vernooij)
 
   * Add porcelain 'list_tags'. (Ryan Faulkner)
 
   * Add porcelain 'push'. (Ryan Faulkner)
 
   * Add porcelain 'pull'. (Ryan Faulkner)
 
   * Support 'http.proxy' in HttpGitClient.
     (Jelmer Vernooij, #1096030)
 
   * Support 'http.useragent' in HttpGitClient.
     (Jelmer Vernooij)
 
   * In server, wait for clients to send empty list of
     wants when talking to empty repository.
     (Damien Tournoud)
 
   * Various changes to improve compatibility with
     Python 3. (Gary van der Merwe)
 
  BUG FIXES
 
   * Support unseekable 'wsgi.input' streams.
     (Jonas Haag)
 
   * Raise TypeError when passing unicode() object
     to Repo.__getitem__.
     (Jonas Haag)
 
   * Fix handling of `reset` command in dulwich.fastexport.
     (Jelmer Vernooij, #1249029)
 
   * In client, don't wait for server to close connection
     first. Fixes hang when used against GitHub
     server implementation. (Siddharth Agarwal)
 
   * DeltaChainIterator: fix a corner case where an object is inflated as an
     object already in the repository.
     (Damien Tournoud, #135)
 
   * Stop leaking file handles during pack reload. (Damien Tournoud)
 
   * Avoid reopening packs during pack cache reload. (Jelmer Vernooij)
 
  API CHANGES
 
   * Drop support for Python 2.6. (Jelmer Vernooij)
 
 0.9.5	2014-02-23
 
  IMPROVEMENTS
 
   * Add porcelain 'tag'. (Ryan Faulkner)
 
   * New module `dulwich.objectspec` for parsing strings referencing
     objects and commit ranges. (Jelmer Vernooij)
 
   * Add shallow branch support. (milki)
 
   * Allow passing urllib2 `opener` into HttpGitClient.
     (Dov Feldstern, #909037)
 
  CHANGES
 
   * Drop support for Python 2.4 and 2.5. (Jelmer Vernooij)
 
  API CHANGES
 
   * Remove long deprecated ``Repo.commit``, ``Repo.get_blob``,
     ``Repo.tree`` and ``Repo.tag``. (Jelmer Vernooij)
 
   * Remove long deprecated ``Repo.revision_history`` and ``Repo.ref``.
     (Jelmer Vernooij)
 
   * Remove long deprecated ``Tree.entries``. (Jelmer Vernooij)
 
  BUG FIXES
 
   * Raise KeyError rather than TypeError when passing in
     unicode object of length 20 or 40 to Repo.__getitem__.
     (Jelmer Vernooij)
 
   * Use 'rm' rather than 'unlink' in tests, since the latter
     does not exist on OpenBSD and other platforms.
     (Dmitrij D. Czarkoff)
 
 0.9.4	2013-11-30
 
  IMPROVEMENTS
 
   * Add ssh_kwargs attribute to ParamikoSSHVendor. (milki)
 
   * Add Repo.set_description(). (Víðir Valberg Guðmundsson)
 
   * Add a basic `dulwich.porcelain` module. (Jelmer Vernooij, Marcin Kuzminski)
 
   * Various performance improvements for object access.
     (Jelmer Vernooij)
 
   * New function `get_transport_and_path_from_url`,
     similar to `get_transport_and_path` but only
     supports URLs.
     (Jelmer Vernooij)
 
   * Add support for file:// URLs in `get_transport_and_path_from_url`.
     (Jelmer Vernooij)
 
   * Add LocalGitClient implementation.
     (Jelmer Vernooij)
 
  BUG FIXES
 
   * Support filesystems with 64bit inode and device numbers.
     (André Roth)
 
  CHANGES
 
   * Ref handling has been moved to dulwich.refs.
     (Jelmer Vernooij)
 
  API CHANGES
 
   * Remove long deprecated RefsContainer.set_ref().
     (Jelmer Vernooij)
 
   * Repo.ref() is now deprecated in favour of Repo.refs[].
     (Jelmer Vernooij)
 
 FEATURES
 
   * Add support for graftpoints. (milki)
 
 0.9.3	2013-09-27
 
  BUG FIXES
 
   * Fix path for stdint.h in MANIFEST.in. (Jelmer Vernooij)
 
 0.9.2	2013-09-26
 
  BUG FIXES
 
   * Include stdint.h in MANIFEST.in (Mark Mikofski)
 
 0.9.1	2013-09-22
 
  BUG FIXES
 
   * Support lookups of 40-character refs in BaseRepo.__getitem__. (Chow Loong Jin, Jelmer Vernooij)
 
   * Fix fetching packs with side-band-64k capability disabled. (David Keijser, Jelmer Vernooij)
 
   * Several fixes in send-pack protocol behaviour - handling of empty pack files and deletes.
     (milki, #1063087)
 
   * Fix capability negotiation when fetching packs over HTTP.
     (#1072461, William Grant)
 
   * Enforce determine_wants returning an empty list rather than None. (Fabien Boucher, Jelmer Vernooij)
 
   * In the server, support pushes just removing refs. (Fabien Boucher, Jelmer Vernooij)
 
  IMPROVEMENTS
 
   * Support passing a single revision to BaseRepo.get_walker() rather than a list of revisions. 
     (Alberto Ruiz)
 
   * Add `Repo.get_description` method. (Jelmer Vernooij)
 
   * Support thin packs in Pack.iterobjects() and Pack.get_raw().
     (William Grant)
 
   * Add `MemoryObjectStore.add_pack` and `MemoryObjectStore.add_thin_pack` methods.
     (David Bennett)
 
   * Add paramiko-based SSH vendor. (Aaron O'Mullan)
 
   * Support running 'dulwich.server' and 'dulwich.web' using 'python -m'.
     (Jelmer Vernooij)
 
   * Add ObjectStore.close(). (Jelmer Vernooij)
 
   * Raise appropriate NotImplementedError when encountering dumb HTTP servers.
     (Jelmer Vernooij)
 
  API CHANGES
 
   * SSHVendor.connect_ssh has been renamed to SSHVendor.run_command.
     (Jelmer Vernooij)
 
   * ObjectStore.add_pack() now returns a 3-tuple. The last element will be an
     abort() method that can be used to cancel the pack operation.
     (Jelmer Vernooij)
 
 0.9.0	2013-05-31
 
  BUG FIXES
 
   * Push efficiency - report missing objects only. (#562676, Artem Tikhomirov)
 
   * Use indentation consistent with C Git in config files.
     (#1031356, Curt Moore, Jelmer Vernooij)
 
   * Recognize and skip binary files in diff function.
     (Takeshi Kanemoto)
 
   * Fix handling of relative paths in dulwich.client.get_transport_and_path.
     (Brian Visel, #1169368)
 
   * Preserve ordering of entries in configuration.
     (Benjamin Pollack)
 
   * Support ~ expansion in SSH client paths. (milki, #1083439)
 
   * Support relative paths in alternate paths.
     (milki, Michel Lespinasse, #1175007)
 
   * Log all error messages from wsgiref server to the logging module. This
     makes the test suit quiet again. (Gary van der Merwe)
 
   * Support passing None for empty tree in changes_from_tree.
     (Kevin Watters)
 
   * Support fetching empty repository in client. (milki, #1060462)
 
  IMPROVEMENTS:
 
   * Add optional honor_filemode flag to build_index_from_tree.
     (Mark Mikofski)
 
   * Support core/filemode setting when building trees. (Jelmer Vernooij)
 
   * Add chapter on tags in tutorial. (Ryan Faulkner)
 
  FEATURES
 
   * Add support for mergetags. (milki, #963525)
 
   * Add support for posix shell hooks. (milki)
 
 0.8.7	2012-11-27
 
  BUG FIXES
 
   * Fix use of alternates in ``DiskObjectStore``.{__contains__,__iter__}.
     (Dmitriy)
 
   * Fix compatibility with Python 2.4. (David Carr)
 
 0.8.6	2012-11-09
 
  API CHANGES
 
   * dulwich.__init__ no longer imports client, protocol, repo and
     server modules. (Jelmer Vernooij)
 
  FEATURES
 
   * ConfigDict now behaves more like a dictionary.
     (Adam 'Cezar' Jenkins, issue #58)
 
   * HTTPGitApplication now takes an optional
     `fallback_app` argument. (Jonas Haag, issue #67)
 
   * Support for large pack index files. (Jameson Nash)
 
  TESTING
 
   * Make index entry tests a little bit less strict, to cope with
     slightly different behaviour on various platforms.
     (Jelmer Vernooij)
 
   * ``setup.py test`` (available when setuptools is installed) now
     runs all tests, not just the basic unit tests.
     (Jelmer Vernooij)
 
  BUG FIXES
 
   * Commit._deserialize now actually deserializes the current state rather than
     the previous one. (Yifan Zhang, issue #59)
 
   * Handle None elements in lists of TreeChange objects. (Alex Holmes)
 
   * Support cloning repositories without HEAD set.
     (D-Key, Jelmer Vernooij, issue #69)
 
   * Support ``MemoryRepo.get_config``. (Jelmer Vernooij)
 
   * In ``get_transport_and_path``, pass extra keyword arguments on to
     HttpGitClient. (Jelmer Vernooij)
 
 0.8.5	2012-03-29
 
  BUG FIXES
 
   * Avoid use of 'with' in dulwich.index. (Jelmer Vernooij)
 
   * Be a little bit strict about OS behaviour in index tests.
     Should fix the tests on Debian GNU/kFreeBSD. (Jelmer Vernooij)
 
 0.8.4	2012-03-28
 
  BUG FIXES
 
   * Options on the same line as sections in config files are now supported.
     (Jelmer Vernooij, #920553)
 
   * Only negotiate capabilities that are also supported by the server.
     (Rod Cloutier, Risto Kankkunen)
 
   * Fix parsing of invalid timezone offsets with two minus signs.
     (Jason R. Coombs, #697828)
 
   * Reset environment variables during tests, to avoid
     test isolation leaks reading ~/.gitconfig. (Risto Kankkunen)
 
  TESTS
 
   * $HOME is now explicitly specified for tests that use it to read
     ``~/.gitconfig``, to prevent test isolation issues.
     (Jelmer Vernooij, #920330)
 
  FEATURES
 
   * Additional arguments to get_transport_and_path are now passed
     on to the constructor of the transport. (Sam Vilain)
 
   * The WSGI server now transparently handles when a git client submits data
     using Content-Encoding: gzip.
     (David Blewett, Jelmer Vernooij)
 
   * Add dulwich.index.build_index_from_tree(). (milki)
 
 0.8.3	2012-01-21
 
  FEATURES
 
   * The config parser now supports the git-config file format as
     described in git-config(1) and can write git config files.
     (Jelmer Vernooij, #531092, #768687)
 
   * ``Repo.do_commit`` will now use the user identity from
     .git/config or ~/.gitconfig if none was explicitly specified.
     (Jelmer Vernooij)
 
  BUG FIXES
 
   * Allow ``determine_wants`` methods to include the zero sha in their
     return value. (Jelmer Vernooij)
 
 0.8.2	2011-12-18
 
  BUG FIXES
 
   * Cope with different zlib buffer sizes in sha1 file parser.
     (Jelmer Vernooij)
 
   * Fix get_transport_and_path for HTTP/HTTPS URLs.
     (Bruno Renié)
 
   * Avoid calling free_objects() on NULL in error cases. (Chris Eberle)
 
   * Fix use --bare argument to 'dulwich init'. (Chris Eberle)
 
   * Properly abort connections when the determine_wants function
     raises an exception. (Jelmer Vernooij, #856769)
 
   * Tweak xcodebuild hack to deal with more error output.
     (Jelmer Vernooij, #903840)
 
  FEATURES
 
   * Add support for retrieving tarballs from remote servers.
     (Jelmer Vernooij, #379087)
 
   * New method ``update_server_info`` which generates data
     for dumb server access. (Jelmer Vernooij, #731235)
 
 0.8.1	2011-10-31
 
  FEATURES
 
   * Repo.do_commit has a new argument 'ref'.
 
   * Repo.do_commit has a new argument 'merge_heads'. (Jelmer Vernooij)
 
   * New ``Repo.get_walker`` method. (Jelmer Vernooij)
 
   * New ``Repo.clone`` method. (Jelmer Vernooij, #725369)
 
   * ``GitClient.send_pack`` now supports the 'side-band-64k' capability.
     (Jelmer Vernooij)
 
   * ``HttpGitClient`` which supports the smart server protocol over
     HTTP. "dumb" access is not yet supported. (Jelmer Vernooij, #373688)
 
   * Add basic support for alternates. (Jelmer Vernooij, #810429)
 
  CHANGES
 
   * unittest2 or python >= 2.7 is now required for the testsuite.
     testtools is no longer supported. (Jelmer Vernooij, #830713)
 
  BUG FIXES
 
   * Fix compilation with older versions of MSVC.  (Martin gz)
 
   * Special case 'refs/stash' as a valid ref. (Jelmer Vernooij, #695577)
 
   * Smart protocol clients can now change refs even if they are
     not uploading new data. (Jelmer Vernooij, #855993)
 
   * Don't compile C extensions when running in pypy.
     (Ronny Pfannschmidt, #881546)
 
   * Use different name for strnlen replacement function to avoid clashing
     with system strnlen. (Jelmer Vernooij, #880362)
 
  API CHANGES
 
   * ``Repo.revision_history`` is now deprecated in favor of ``Repo.get_walker``.
     (Jelmer Vernooij)
 
 0.8.0	2011-08-07
 
  FEATURES
 
   * New DeltaChainIterator abstract class for quickly iterating all objects in
     a pack, with implementations for pack indexing and inflation.
     (Dave Borowitz)
 
   * New walk module with a Walker class for customizable commit walking.
     (Dave Borowitz)
 
   * New tree_changes_for_merge function in diff_tree. (Dave Borowitz)
 
   * Easy rename detection in RenameDetector even without find_copies_harder.
     (Dave Borowitz)
 
  BUG FIXES
 
   * Avoid storing all objects in memory when writing pack.
     (Jelmer Vernooij, #813268)
 
   * Support IPv6 for git:// connections. (Jelmer Vernooij, #801543)
 
   * Improve performance of Repo.revision_history(). (Timo Schmid, #535118)
 
   * Fix use of SubprocessWrapper on Windows. (Paulo Madeira, #670035)
 
   * Fix compilation on newer versions of Mac OS X (Lion and up). (Ryan McKern, #794543)
 
   * Prevent raising ValueError for correct refs in RefContainer.__delitem__.
 
   * Correctly return a tuple from MemoryObjectStore.get_raw. (Dave Borowitz)
 
   * Fix a bug in reading the pack checksum when there are fewer than 20 bytes
     left in the buffer. (Dave Borowitz)
 
   * Support ~ in git:// URL paths. (Jelmer Vernooij, #813555)
 
   * Make ShaFile.__eq__ work when other is not a ShaFile. (Dave Borowitz)
 
   * ObjectStore.get_graph_walker() now no longer yields the same
     revision more than once. This has a significant improvement for
     performance when wide revision graphs are involved.
     (Jelmer Vernooij, #818168)
 
   * Teach ReceivePackHandler how to read empty packs. (Dave Borowitz)
 
   * Don't send a pack with duplicates of the same object. (Dave Borowitz)
 
   * Teach the server how to serve a clone of an empty repo. (Dave Borowitz)
 
   * Correctly advertise capabilities during receive-pack. (Dave Borowitz)
 
   * Fix add/add and add/rename conflicts in tree_changes_for_merge.
     (Dave Borowitz)
 
   * Use correct MIME types in web server. (Dave Borowitz)
 
  API CHANGES
 
   * write_pack no longer takes the num_objects argument and requires an object
     to be passed in that is iterable (rather than an iterator) and that
     provides __len__.  (Jelmer Vernooij)
 
   * write_pack_data has been renamed to write_pack_objects and no longer takes a
     num_objects argument. (Jelmer Vernooij)
 
   * take_msb_bytes, read_zlib_chunks, unpack_objects, and
     PackStreamReader.read_objects now take an additional argument indicating a
     crc32 to compute. (Dave Borowitz)
 
   * PackObjectIterator was removed; its functionality is still exposed by
     PackData.iterobjects. (Dave Borowitz)
 
   * Add a sha arg to write_pack_object to incrementally compute a SHA.
     (Dave Borowitz)
 
   * Include offset in PackStreamReader results. (Dave Borowitz)
 
   * Move PackStreamReader from server to pack. (Dave Borowitz)
 
   * Extract a check_length_and_checksum, compute_file_sha, and
     pack_object_header pack helper functions. (Dave Borowitz)
 
   * Extract a compute_file_sha function. (Dave Borowitz)
 
   * Remove move_in_thin_pack as a separate method; add_thin_pack now completes
     the thin pack and moves it in in one step. Remove ThinPackData as well.
     (Dave Borowitz)
 
   * Custom buffer size in read_zlib_chunks. (Dave Borowitz)
 
   * New UnpackedObject data class that replaces ad-hoc tuples in the return
     value of unpack_object and various DeltaChainIterator methods.
     (Dave Borowitz)
 
   * Add a lookup_path convenience method to Tree. (Dave Borowitz)
 
   * Optionally create RenameDetectors without passing in tree SHAs.
     (Dave Borowitz)
 
   * Optionally include unchanged entries in RenameDetectors. (Dave Borowitz)
 
   * Optionally pass a RenameDetector to tree_changes. (Dave Borowitz)
 
   * Optionally pass a request object through to server handlers. (Dave Borowitz)
 
  TEST CHANGES
 
   * If setuptools is installed, "python setup.py test" will now run the testsuite.
     (Jelmer Vernooij)
 
   * Add a new build_pack test utility for building packs from a simple spec.
     (Dave Borowitz)
 
   * Add a new build_commit_graph test utility for building commits from a
     simple spec. (Dave Borowitz)
 
 0.7.1	2011-04-12
 
  BUG FIXES
 
   * Fix double decref in _diff_tree.c. (Ted Horst, #715528)
 
   * Fix the build on Windows. (Pascal Quantin)
 
   * Fix get_transport_and_path compatibility with pre-2.6.5 versions of Python.
     (Max Bowsher, #707438)
 
   * BaseObjectStore.determine_wants_all no longer breaks on zero SHAs.
     (Jelmer Vernooij)
 
   * write_tree_diff() now supports submodules.
     (Jelmer Vernooij)
 
   * Fix compilation for XCode 4 and older versions of distutils.sysconfig.
     (Daniele Sluijters)
 
  IMPROVEMENTS
 
   * Sphinxified documentation. (Lukasz Balcerzak)
 
   * Add Pack.keep.(Marc Brinkmann)
 
  API CHANGES
 
   * The order of the parameters to Tree.add(name, mode, sha) has changed, and
     is now consistent with the rest of Dulwich. Existing code will still
     work but print a DeprecationWarning. (Jelmer Vernooij, #663550)
 
   * Tree.entries() is now deprecated in favour of Tree.items() and
     Tree.iteritems(). (Jelmer Vernooij)
 
 0.7.0	2011-01-21
 
  FEATURES
 
   * New `dulwich.diff_tree` module for simple content-based rename detection.
     (Dave Borowitz)
 
   * Add Tree.items(). (Jelmer Vernooij)
 
   * Add eof() and unread_pkt_line() methods to Protocol. (Dave Borowitz)
 
   * Add write_tree_diff(). (Jelmer Vernooij)
 
   * Add `serve_command` function for git server commands as executables.
     (Jelmer Vernooij)
 
   * dulwich.client.get_transport_and_path now supports rsync-style repository URLs.
     (Dave Borowitz, #568493)
 
  BUG FIXES
 
   * Correct short-circuiting operation for no-op fetches in the server.
     (Dave Borowitz)
 
   * Support parsing git mbox patches without a version tail, as generated by
     Mercurial.  (Jelmer Vernooij)
 
   * Fix dul-receive-pack and dul-upload-pack. (Jelmer Vernooij)
 
   * Zero-padded file modes in Tree objects no longer trigger an exception but
     the check code warns about them. (Augie Fackler, #581064)
 
   * Repo.init() now honors the mkdir flag. (#671159)
 
   * The ref format is now checked when setting a ref rather than when reading it back.
     (Dave Borowitz, #653527)
 
   * Make sure pack files are closed correctly. (Tay Ray Chuan)
 
  DOCUMENTATION
 
   * Run the tutorial inside the test suite. (Jelmer Vernooij)
 
   * Reorganized and updated the tutorial. (Jelmer Vernooij, Dave Borowitz, #610550,
      #610540)
 
 
 0.6.2	2010-10-16
 
  BUG FIXES
 
   * HTTP server correctly handles empty CONTENT_LENGTH. (Dave Borowitz)
 
   * Don't error when creating GitFiles with the default mode. (Dave Borowitz)
 
   * ThinPackData.from_file now works with resolve_ext_ref callback.
     (Dave Borowitz)
 
   * Provide strnlen() on mingw32 which doesn't have it. (Hans Kolek)
 
   * Set bare=true in the configuratin for bare repositories. (Dirk Neumann)
 
  FEATURES
 
   * Use slots for core objects to save up on memory. (Jelmer Vernooij)
 
   * Web server supports streaming progress/pack output. (Dave Borowitz)
 
   * New public function dulwich.pack.write_pack_header. (Dave Borowitz)
 
   * Distinguish between missing files and read errors in HTTP server.
     (Dave Borowitz)
 
   * Initial work on support for fastimport using python-fastimport.
     (Jelmer Vernooij)
 
   * New dulwich.pack.MemoryPackIndex class. (Jelmer Vernooij)
 
   * Delegate SHA peeling to the object store.  (Dave Borowitz)
 
  TESTS
 
   * Use GitFile when modifying packed-refs in tests. (Dave Borowitz)
 
   * New tests in test_web with better coverage and fewer ad-hoc mocks.
     (Dave Borowitz)
 
   * Standardize quote delimiters in test_protocol. (Dave Borowitz)
 
   * Fix use when testtools is installed. (Jelmer Vernooij)
 
   * Add trivial test for write_pack_header. (Jelmer Vernooij)
 
   * Refactor some of dulwich.tests.compat.server_utils. (Dave Borowitz)
 
   * Allow overwriting id property of objects in test utils. (Dave Borowitz)
 
   * Use real in-memory objects rather than stubs for server tests.
     (Dave Borowitz)
 
   * Clean up MissingObjectFinder. (Dave Borowitz)
 
  API CHANGES
 
   * ObjectStore.iter_tree_contents now walks contents in depth-first, sorted
     order. (Dave Borowitz)
 
   * ObjectStore.iter_tree_contents can optionally yield tree objects as well.
     (Dave Borowitz).
 
   * Add side-band-64k support to ReceivePackHandler. (Dave Borowitz)
 
   * Change server capabilities methods to classmethods. (Dave Borowitz)
 
   * Tweak server handler injection. (Dave Borowitz)
 
   * PackIndex1 and PackIndex2 now subclass FilePackIndex, which is 
     itself a subclass of PackIndex. (Jelmer Vernooij)
 
  DOCUMENTATION
 
   * Add docstrings for various functions in dulwich.objects. (Jelmer Vernooij)
 
   * Clean up docstrings in dulwich.protocol. (Dave Borowitz)
 
   * Explicitly specify allowed protocol commands to
     ProtocolGraphWalker.read_proto_line.  (Dave Borowitz)
 
   * Add utility functions to DictRefsContainer. (Dave Borowitz)
 
 
 0.6.1	2010-07-22
 
  BUG FIXES
 
   * Fix memory leak in C implementation of sorted_tree_items. (Dave Borowitz)
 
   * Use correct path separators for named repo files. (Dave Borowitz)
 
   * python > 2.7 and testtools-based test runners will now also pick up skipped
     tests correctly. (Jelmer Vernooij)
 
  FEATURES
 
   * Move named file initilization to BaseRepo. (Dave Borowitz)
 
   * Add logging utilities and git/HTTP server logging. (Dave Borowitz)
 
   * The GitClient interface has been cleaned up and instances are now reusable.
     (Augie Fackler)
 
   * Allow overriding paths to executables in GitSSHClient. 
     (Ross Light, Jelmer Vernooij, #585204)
 
   * Add PackBasedObjectStore.pack_loose_objects(). (Jelmer Vernooij)
 
  TESTS
 
   * Add tests for sorted_tree_items and C implementation. (Dave Borowitz)
 
   * Add a MemoryRepo that stores everything in memory. (Dave Borowitz)
 
   * Quiet logging output from web tests. (Dave Borowitz)
 
   * More flexible version checking for compat tests. (Dave Borowitz)
 
   * Compat tests for servers with and without side-band-64k. (Dave Borowitz)
 
  CLEANUP
 
   * Clean up file headers. (Dave Borowitz)
 
  TESTS
 
   * Use GitFile when modifying packed-refs in tests. (Dave Borowitz)
 
  API CHANGES
 
   * dulwich.pack.write_pack_index_v{1,2} now take a file-like object
     rather than a filename. (Jelmer Vernooij)
 
   * Make dul-daemon/dul-web trivial wrappers around server functionality.
     (Dave Borowitz)
 
   * Move reference WSGI handler to web.py. (Dave Borowitz)
 
   * Factor out _report_status in ReceivePackHandler. (Dave Borowitz)
 
   * Factor out a function to convert a line to a pkt-line. (Dave Borowitz)
 
 
 0.6.0	2010-05-22
 
 note: This list is most likely incomplete for 0.6.0.
 
  BUG FIXES
  
   * Fix ReceivePackHandler to disallow removing refs without delete-refs.
     (Dave Borowitz)
 
   * Deal with capabilities required by the client, even if they 
     can not be disabled in the server. (Dave Borowitz)
 
   * Fix trailing newlines in generated patch files.
     (Jelmer Vernooij)
 
   * Implement RefsContainer.__contains__. (Jelmer Vernooij)
 
   * Cope with \r in ref files on Windows. (
     http://github.com/jelmer/dulwich/issues/#issue/13, Jelmer Vernooij)
 
   * Fix GitFile breakage on Windows. (Anatoly Techtonik, #557585)
 
   * Support packed ref deletion with no peeled refs. (Augie Fackler)
 
   * Fix send pack when there is nothing to fetch. (Augie Fackler)
 
   * Fix fetch if no progress function is specified. (Augie Fackler)
 
   * Allow double-staging of files that are deleted in the index. 
     (Dave Borowitz)
 
   * Fix RefsContainer.add_if_new to support dangling symrefs.
     (Dave Borowitz)
 
   * Non-existant index files in non-bare repositories are now treated as 
     empty. (Dave Borowitz)
 
   * Always update ShaFile.id when the contents of the object get changed. 
     (Jelmer Vernooij)
 
   * Various Python2.4-compatibility fixes. (Dave Borowitz)
 
   * Fix thin pack handling. (Dave Borowitz)
  
  FEATURES
 
   * Add include-tag capability to server. (Dave Borowitz)
 
   * New dulwich.fastexport module that can generate fastexport 
     streams. (Jelmer Vernooij)
 
   * Implemented BaseRepo.__contains__. (Jelmer Vernooij)
 
   * Add __setitem__ to DictRefsContainer. (Dave Borowitz)
 
   * Overall improvements checking Git objects. (Dave Borowitz)
 
   * Packs are now verified while they are received. (Dave Borowitz)
 
  TESTS
 
   * Add framework for testing compatibility with C Git. (Dave Borowitz)
 
   * Add various tests for the use of non-bare repositories. (Dave Borowitz)
 
   * Cope with diffstat not being available on all platforms. 
     (Tay Ray Chuan, Jelmer Vernooij)
 
   * Add make_object and make_commit convenience functions to test utils.
     (Dave Borowitz)
 
  API BREAKAGES
 
   * The 'committer' and 'message' arguments to Repo.do_commit() have 
     been swapped. 'committer' is now optional. (Jelmer Vernooij)
 
   * Repo.get_blob, Repo.commit, Repo.tag and Repo.tree are now deprecated.
     (Jelmer Vernooij)
 
   * RefsContainer.set_ref() was renamed to RefsContainer.set_symbolic_ref(),
     for clarity. (Jelmer Vernooij)
 
  API CHANGES
 
   * The primary serialization APIs in dulwich.objects now work 
     with chunks of strings rather than with full-text strings. 
     (Jelmer Vernooij)
 
 0.5.02010-03-03
 
  BUG FIXES
 
   * Support custom fields in commits (readonly). (Jelmer Vernooij)
 
   * Improved ref handling. (Dave Borowitz)
 
   * Rework server protocol to be smarter and interoperate with cgit client.
     (Dave Borowitz)
 
   * Add a GitFile class that uses the same locking protocol for writes as 
     cgit. (Dave Borowitz)
 
   * Cope with forward slashes correctly in the index on Windows.
     (Jelmer Vernooij, #526793)
 
  FEATURES
 
   * --pure option to setup.py to allow building/installing without the C 
     extensions. (Hal Wine, Anatoly Techtonik, Jelmer Vernooij, #434326)
 
   * Implement Repo.get_config(). (Jelmer Vernooij, Augie Fackler)
 
   * HTTP dumb and smart server. (Dave Borowitz)
 
   * Add abstract baseclass for Repo that does not require file system 
     operations. (Dave Borowitz)
 
 0.4.1	2010-01-03
 
  FEATURES
 
   * Add ObjectStore.iter_tree_contents(). (Jelmer Vernooij)
 
   * Add Index.changes_from_tree(). (Jelmer Vernooij)
 
   * Add ObjectStore.tree_changes(). (Jelmer Vernooij)
 
   * Add functionality for writing patches in dulwich.patch.
     (Jelmer Vernooij)
 
 0.4.0	2009-10-07
 
  DOCUMENTATION
 
   * Added tutorial.
 
  API CHANGES
 
   * dulwich.object_store.tree_lookup_path will now return the mode and 
     sha of the object found rather than the object itself.
 
  BUG FIXES
 
   * Use binascii.hexlify / binascii.unhexlify for better performance.
 
   * Cope with extra unknown data in index files by ignoring it (for now).
 
   * Add proper error message when server unexpectedly hangs up. (#415843)
 
   * Correctly write opcode for equal in create_delta.
 
 0.3.3	2009-07-23
 
  FEATURES
 
   * Implement ShaFile.__hash__().
 
   * Implement Tree.__len__()
 
  BUG FIXES
   
   * Check for 'objects' and 'refs' directories
     when looking for a Git repository. (#380818)
 
 0.3.2	2009-05-20
 
  BUG FIXES
 
   * Support the encoding field in Commits.
   
   * Some Windows compatibility fixes.
 
   * Fixed several issues in commit support.
 
  FEATURES
 
   * Basic support for handling submodules.
 
 0.3.1	2009-05-13
 
  FEATURES
 
   * Implemented Repo.__getitem__, Repo.__setitem__ and Repo.__delitem__ to 
     access content.
 
  API CHANGES
 
   * Removed Repo.set_ref, Repo.remove_ref, Repo.tags, Repo.get_refs and 
     Repo.heads in favor of Repo.refs, a dictionary-like object for accessing
     refs.
 
  BUG FIXES
 
   * Removed import of 'sha' module in objects.py, which was causing 
     deprecation warnings on Python 2.6.
 
 0.3.0	2009-05-10
 
  FEATURES
 
   * A new function 'commit_tree' has been added that can commit a tree 
     based on an index.
 
  BUG FIXES
 
   * The memory usage when generating indexes has been significantly reduced.
  
   * A memory leak in the C implementation of parse_tree has been fixed.
 
   * The send-pack smart server command now works. (Thanks Scott Chacon)
 
   * The handling of short timestamps (less than 10 digits) has been fixed.
 
   * The handling of timezones has been fixed.
 
 0.2.1	2009-04-30
 
  BUG FIXES
 
   * Fix compatibility with Python2.4.
 
 0.2.0	2009-04-30
 
  FEATURES
 
   * Support for activity reporting in smart protocol client.
 
   * Optional C extensions for better performance in a couple of 
     places that are performance-critical.
 
 0.1.1	2009-03-13
 
  BUG FIXES
 
   * Fixed regression in Repo.find_missing_objects()
 
   * Don't fetch ^{} objects from remote hosts, as requesting them 
     causes a hangup.
 
   * Always write pack to disk completely before calculating checksum.
 
  FEATURES
 
   * Allow disabling thin packs when talking to remote hosts.
 
 0.1.0	2009-01-24
 
   * Initial release.
diff --git a/dulwich/repo.py b/dulwich/repo.py
index 29b0e669..487feefc 100644
--- a/dulwich/repo.py
+++ b/dulwich/repo.py
@@ -1,1704 +1,1707 @@
 # repo.py -- For dealing with git repositories.
 # Copyright (C) 2007 James Westby <jw+debian@jameswestby.net>
 # Copyright (C) 2008-2013 Jelmer Vernooij <jelmer@jelmer.uk>
 #
 # Dulwich is dual-licensed under the Apache License, Version 2.0 and the GNU
 # General Public License as public by the Free Software Foundation; version 2.0
 # or (at your option) any later version. You can redistribute it and/or
 # modify it under the terms of either of these two licenses.
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
 # You should have received a copy of the licenses; if not, see
 # <http://www.gnu.org/licenses/> for a copy of the GNU General Public License
 # and <http://www.apache.org/licenses/LICENSE-2.0> for a copy of the Apache
 # License, Version 2.0.
 #
 
 
 """Repository access.
 
 This module contains the base class for git repositories
 (BaseRepo) and an implementation which uses a repository on
 local disk (Repo).
 
 """
 
 from io import BytesIO
 import os
 import sys
 import stat
 import time
 from typing import Optional, Tuple, TYPE_CHECKING, List, Dict, Union, Iterable
 
 if TYPE_CHECKING:
     # There are no circular imports here, but we try to defer imports as long
     # as possible to reduce start-up time for anything that doesn't need
     # these imports.
     from dulwich.config import StackedConfig, ConfigFile
     from dulwich.index import Index
 
 from dulwich.errors import (
     NoIndexPresent,
     NotBlobError,
     NotCommitError,
     NotGitRepository,
     NotTreeError,
     NotTagError,
     CommitError,
     RefFormatError,
     HookError,
 )
 from dulwich.file import (
     GitFile,
 )
 from dulwich.object_store import (
     DiskObjectStore,
     MemoryObjectStore,
     BaseObjectStore,
     ObjectStoreGraphWalker,
 )
 from dulwich.objects import (
     check_hexsha,
     valid_hexsha,
     Blob,
     Commit,
     ShaFile,
     Tag,
     Tree,
 )
 from dulwich.pack import (
     pack_objects_to_data,
 )
 
 from dulwich.hooks import (
     Hook,
     PreCommitShellHook,
     PostCommitShellHook,
     CommitMsgShellHook,
     PostReceiveShellHook,
 )
 
 from dulwich.line_ending import BlobNormalizer, TreeBlobNormalizer
 
 from dulwich.refs import (  # noqa: F401
     ANNOTATED_TAG_SUFFIX,
     check_ref_format,
     RefsContainer,
     DictRefsContainer,
     InfoRefsContainer,
     DiskRefsContainer,
     read_packed_refs,
     read_packed_refs_with_peeled,
     write_packed_refs,
     SYMREF,
 )
 
 
 import warnings
 
 
 CONTROLDIR = ".git"
 OBJECTDIR = "objects"
 REFSDIR = "refs"
 REFSDIR_TAGS = "tags"
 REFSDIR_HEADS = "heads"
 INDEX_FILENAME = "index"
 COMMONDIR = "commondir"
 GITDIR = "gitdir"
 WORKTREES = "worktrees"
 
 BASE_DIRECTORIES = [
     ["branches"],
     [REFSDIR],
     [REFSDIR, REFSDIR_TAGS],
     [REFSDIR, REFSDIR_HEADS],
     ["hooks"],
     ["info"],
 ]
 
 DEFAULT_REF = b"refs/heads/master"
 
 
 class InvalidUserIdentity(Exception):
     """User identity is not of the format 'user <email>'"""
 
     def __init__(self, identity):
         self.identity = identity
 
 
 def _get_default_identity() -> Tuple[str, str]:
     import getpass
     import socket
 
     username = getpass.getuser()
     try:
         import pwd
     except ImportError:
         fullname = None
     else:
         try:
             gecos = pwd.getpwnam(username).pw_gecos
         except KeyError:
             fullname = None
         else:
-            fullname = gecos.split(",")[0]
+            if gecos:
+                fullname = gecos.split(",")[0]
+            else:
+                fullname = None
     if not fullname:
         fullname = username
     email = os.environ.get("EMAIL")
     if email is None:
         email = "{}@{}".format(username, socket.gethostname())
     return (fullname, email)
 
 
 def get_user_identity(config: "StackedConfig", kind: Optional[str] = None) -> bytes:
     """Determine the identity to use for new commits.
 
     If kind is set, this first checks
     GIT_${KIND}_NAME and GIT_${KIND}_EMAIL.
 
     If those variables are not set, then it will fall back
     to reading the user.name and user.email settings from
     the specified configuration.
 
     If that also fails, then it will fall back to using
     the current users' identity as obtained from the host
     system (e.g. the gecos field, $EMAIL, $USER@$(hostname -f).
 
     Args:
       kind: Optional kind to return identity for,
         usually either "AUTHOR" or "COMMITTER".
 
     Returns:
       A user identity
     """
     user = None  # type: Optional[bytes]
     email = None  # type: Optional[bytes]
     if kind:
         user_uc = os.environ.get("GIT_" + kind + "_NAME")
         if user_uc is not None:
             user = user_uc.encode("utf-8")
         email_uc = os.environ.get("GIT_" + kind + "_EMAIL")
         if email_uc is not None:
             email = email_uc.encode("utf-8")
     if user is None:
         try:
             user = config.get(("user",), "name")
         except KeyError:
             user = None
     if email is None:
         try:
             email = config.get(("user",), "email")
         except KeyError:
             email = None
     default_user, default_email = _get_default_identity()
     if user is None:
         user = default_user.encode("utf-8")
     if email is None:
         email = default_email.encode("utf-8")
     if email.startswith(b"<") and email.endswith(b">"):
         email = email[1:-1]
     return user + b" <" + email + b">"
 
 
 def check_user_identity(identity):
     """Verify that a user identity is formatted correctly.
 
     Args:
       identity: User identity bytestring
     Raises:
       InvalidUserIdentity: Raised when identity is invalid
     """
     try:
         fst, snd = identity.split(b" <", 1)
     except ValueError:
         raise InvalidUserIdentity(identity)
     if b">" not in snd:
         raise InvalidUserIdentity(identity)
 
 
 def parse_graftpoints(
     graftpoints: Iterable[bytes],
 ) -> Dict[bytes, List[bytes]]:
     """Convert a list of graftpoints into a dict
 
     Args:
       graftpoints: Iterator of graftpoint lines
 
     Each line is formatted as:
         <commit sha1> <parent sha1> [<parent sha1>]*
 
     Resulting dictionary is:
         <commit sha1>: [<parent sha1>*]
 
     https://git.wiki.kernel.org/index.php/GraftPoint
     """
     grafts = {}
     for line in graftpoints:
         raw_graft = line.split(None, 1)
 
         commit = raw_graft[0]
         if len(raw_graft) == 2:
             parents = raw_graft[1].split()
         else:
             parents = []
 
         for sha in [commit] + parents:
             check_hexsha(sha, "Invalid graftpoint")
 
         grafts[commit] = parents
     return grafts
 
 
 def serialize_graftpoints(graftpoints: Dict[bytes, List[bytes]]) -> bytes:
     """Convert a dictionary of grafts into string
 
     The graft dictionary is:
         <commit sha1>: [<parent sha1>*]
 
     Each line is formatted as:
         <commit sha1> <parent sha1> [<parent sha1>]*
 
     https://git.wiki.kernel.org/index.php/GraftPoint
 
     """
     graft_lines = []
     for commit, parents in graftpoints.items():
         if parents:
             graft_lines.append(commit + b" " + b" ".join(parents))
         else:
             graft_lines.append(commit)
     return b"\n".join(graft_lines)
 
 
 def _set_filesystem_hidden(path):
     """Mark path as to be hidden if supported by platform and filesystem.
 
     On win32 uses SetFileAttributesW api:
     <https://docs.microsoft.com/windows/desktop/api/fileapi/nf-fileapi-setfileattributesw>
     """
     if sys.platform == "win32":
         import ctypes
         from ctypes.wintypes import BOOL, DWORD, LPCWSTR
 
         FILE_ATTRIBUTE_HIDDEN = 2
         SetFileAttributesW = ctypes.WINFUNCTYPE(BOOL, LPCWSTR, DWORD)(
             ("SetFileAttributesW", ctypes.windll.kernel32)
         )
 
         if isinstance(path, bytes):
             path = os.fsdecode(path)
         if not SetFileAttributesW(path, FILE_ATTRIBUTE_HIDDEN):
             pass  # Could raise or log `ctypes.WinError()` here
 
     # Could implement other platform specific filesytem hiding here
 
 
 class ParentsProvider(object):
     def __init__(self, store, grafts={}, shallows=[]):
         self.store = store
         self.grafts = grafts
         self.shallows = set(shallows)
 
     def get_parents(self, commit_id, commit=None):
         try:
             return self.grafts[commit_id]
         except KeyError:
             pass
         if commit_id in self.shallows:
             return []
         if commit is None:
             commit = self.store[commit_id]
         return commit.parents
 
 
 class BaseRepo(object):
     """Base class for a git repository.
 
     :ivar object_store: Dictionary-like object for accessing
         the objects
     :ivar refs: Dictionary-like object with the refs in this
         repository
     """
 
     def __init__(self, object_store: BaseObjectStore, refs: RefsContainer):
         """Open a repository.
 
         This shouldn't be called directly, but rather through one of the
         base classes, such as MemoryRepo or Repo.
 
         Args:
           object_store: Object store to use
           refs: Refs container to use
         """
         self.object_store = object_store
         self.refs = refs
 
         self._graftpoints = {}  # type: Dict[bytes, List[bytes]]
         self.hooks = {}  # type: Dict[str, Hook]
 
     def _determine_file_mode(self) -> bool:
         """Probe the file-system to determine whether permissions can be trusted.
 
         Returns: True if permissions can be trusted, False otherwise.
         """
         raise NotImplementedError(self._determine_file_mode)
 
     def _init_files(self, bare: bool) -> None:
         """Initialize a default set of named files."""
         from dulwich.config import ConfigFile
 
         self._put_named_file("description", b"Unnamed repository")
         f = BytesIO()
         cf = ConfigFile()
         cf.set("core", "repositoryformatversion", "0")
         if self._determine_file_mode():
             cf.set("core", "filemode", True)
         else:
             cf.set("core", "filemode", False)
 
         cf.set("core", "bare", bare)
         cf.set("core", "logallrefupdates", True)
         cf.write_to_file(f)
         self._put_named_file("config", f.getvalue())
         self._put_named_file(os.path.join("info", "exclude"), b"")
 
     def get_named_file(self, path):
         """Get a file from the control dir with a specific name.
 
         Although the filename should be interpreted as a filename relative to
         the control dir in a disk-based Repo, the object returned need not be
         pointing to a file in that location.
 
         Args:
           path: The path to the file, relative to the control dir.
         Returns: An open file object, or None if the file does not exist.
         """
         raise NotImplementedError(self.get_named_file)
 
     def _put_named_file(self, path, contents):
         """Write a file to the control dir with the given name and contents.
 
         Args:
           path: The path to the file, relative to the control dir.
           contents: A string to write to the file.
         """
         raise NotImplementedError(self._put_named_file)
 
     def _del_named_file(self, path):
         """Delete a file in the contrl directory with the given name."""
         raise NotImplementedError(self._del_named_file)
 
     def open_index(self):
         """Open the index for this repository.
 
         Raises:
           NoIndexPresent: If no index is present
         Returns: The matching `Index`
         """
         raise NotImplementedError(self.open_index)
 
     def fetch(self, target, determine_wants=None, progress=None, depth=None):
         """Fetch objects into another repository.
 
         Args:
           target: The target repository
           determine_wants: Optional function to determine what refs to
             fetch.
           progress: Optional progress function
           depth: Optional shallow fetch depth
         Returns: The local refs
         """
         if determine_wants is None:
             determine_wants = target.object_store.determine_wants_all
         count, pack_data = self.fetch_pack_data(
             determine_wants,
             target.get_graph_walker(),
             progress=progress,
             depth=depth,
         )
         target.object_store.add_pack_data(count, pack_data, progress)
         return self.get_refs()
 
     def fetch_pack_data(
         self,
         determine_wants,
         graph_walker,
         progress,
         get_tagged=None,
         depth=None,
     ):
         """Fetch the pack data required for a set of revisions.
 
         Args:
           determine_wants: Function that takes a dictionary with heads
             and returns the list of heads to fetch.
           graph_walker: Object that can iterate over the list of revisions
             to fetch and has an "ack" method that will be called to acknowledge
             that a revision is present.
           progress: Simple progress function that will be called with
             updated progress strings.
           get_tagged: Function that returns a dict of pointed-to sha ->
             tag sha for including tags.
           depth: Shallow fetch depth
         Returns: count and iterator over pack data
         """
         # TODO(jelmer): Fetch pack data directly, don't create objects first.
         objects = self.fetch_objects(
             determine_wants, graph_walker, progress, get_tagged, depth=depth
         )
         return pack_objects_to_data(objects)
 
     def fetch_objects(
         self,
         determine_wants,
         graph_walker,
         progress,
         get_tagged=None,
         depth=None,
     ):
         """Fetch the missing objects required for a set of revisions.
 
         Args:
           determine_wants: Function that takes a dictionary with heads
             and returns the list of heads to fetch.
           graph_walker: Object that can iterate over the list of revisions
             to fetch and has an "ack" method that will be called to acknowledge
             that a revision is present.
           progress: Simple progress function that will be called with
             updated progress strings.
           get_tagged: Function that returns a dict of pointed-to sha ->
             tag sha for including tags.
           depth: Shallow fetch depth
         Returns: iterator over objects, with __len__ implemented
         """
         if depth not in (None, 0):
             raise NotImplementedError("depth not supported yet")
 
         refs = {}
         for ref, sha in self.get_refs().items():
             try:
                 obj = self.object_store[sha]
             except KeyError:
                 warnings.warn(
                     "ref %s points at non-present sha %s"
                     % (ref.decode("utf-8", "replace"), sha.decode("ascii")),
                     UserWarning,
                 )
                 continue
             else:
                 if isinstance(obj, Tag):
                     refs[ref + ANNOTATED_TAG_SUFFIX] = obj.object[1]
                 refs[ref] = sha
 
         wants = determine_wants(refs)
         if not isinstance(wants, list):
             raise TypeError("determine_wants() did not return a list")
 
         shallows = getattr(graph_walker, "shallow", frozenset())
         unshallows = getattr(graph_walker, "unshallow", frozenset())
 
         if wants == []:
             # TODO(dborowitz): find a way to short-circuit that doesn't change
             # this interface.
 
             if shallows or unshallows:
                 # Do not send a pack in shallow short-circuit path
                 return None
 
             return []
 
         # If the graph walker is set up with an implementation that can
         # ACK/NAK to the wire, it will write data to the client through
         # this call as a side-effect.
         haves = self.object_store.find_common_revisions(graph_walker)
 
         # Deal with shallow requests separately because the haves do
         # not reflect what objects are missing
         if shallows or unshallows:
             # TODO: filter the haves commits from iter_shas. the specific
             # commits aren't missing.
             haves = []
 
         parents_provider = ParentsProvider(self.object_store, shallows=shallows)
 
         def get_parents(commit):
             return parents_provider.get_parents(commit.id, commit)
 
         return self.object_store.iter_shas(
             self.object_store.find_missing_objects(
                 haves,
                 wants,
                 self.get_shallow(),
                 progress,
                 get_tagged,
                 get_parents=get_parents,
             )
         )
 
     def generate_pack_data(self, have, want, progress=None, ofs_delta=None):
         """Generate pack data objects for a set of wants/haves.
 
         Args:
           have: List of SHA1s of objects that should not be sent
           want: List of SHA1s of objects that should be sent
           ofs_delta: Whether OFS deltas can be included
           progress: Optional progress reporting method
         """
         return self.object_store.generate_pack_data(
             have,
             want,
             shallow=self.get_shallow(),
             progress=progress,
             ofs_delta=ofs_delta,
         )
 
     def get_graph_walker(self, heads=None):
         """Retrieve a graph walker.
 
         A graph walker is used by a remote repository (or proxy)
         to find out which objects are present in this repository.
 
         Args:
           heads: Repository heads to use (optional)
         Returns: A graph walker object
         """
         if heads is None:
             heads = [
                 sha
                 for sha in self.refs.as_dict(b"refs/heads").values()
                 if sha in self.object_store
             ]
         parents_provider = ParentsProvider(self.object_store)
         return ObjectStoreGraphWalker(
             heads, parents_provider.get_parents, shallow=self.get_shallow()
         )
 
     def get_refs(self) -> Dict[bytes, bytes]:
         """Get dictionary with all refs.
 
         Returns: A ``dict`` mapping ref names to SHA1s
         """
         return self.refs.as_dict()
 
     def head(self) -> bytes:
         """Return the SHA1 pointed at by HEAD."""
         return self.refs[b"HEAD"]
 
     def _get_object(self, sha, cls):
         assert len(sha) in (20, 40)
         ret = self.get_object(sha)
         if not isinstance(ret, cls):
             if cls is Commit:
                 raise NotCommitError(ret)
             elif cls is Blob:
                 raise NotBlobError(ret)
             elif cls is Tree:
                 raise NotTreeError(ret)
             elif cls is Tag:
                 raise NotTagError(ret)
             else:
                 raise Exception(
                     "Type invalid: %r != %r" % (ret.type_name, cls.type_name)
                 )
         return ret
 
     def get_object(self, sha: bytes) -> ShaFile:
         """Retrieve the object with the specified SHA.
 
         Args:
           sha: SHA to retrieve
         Returns: A ShaFile object
         Raises:
           KeyError: when the object can not be found
         """
         return self.object_store[sha]
 
     def parents_provider(self):
         return ParentsProvider(
             self.object_store,
             grafts=self._graftpoints,
             shallows=self.get_shallow(),
         )
 
     def get_parents(self, sha: bytes, commit: Commit = None) -> List[bytes]:
         """Retrieve the parents of a specific commit.
 
         If the specific commit is a graftpoint, the graft parents
         will be returned instead.
 
         Args:
           sha: SHA of the commit for which to retrieve the parents
           commit: Optional commit matching the sha
         Returns: List of parents
         """
         return self.parents_provider().get_parents(sha, commit)
 
     def get_config(self):
         """Retrieve the config object.
 
         Returns: `ConfigFile` object for the ``.git/config`` file.
         """
         raise NotImplementedError(self.get_config)
 
     def get_description(self):
         """Retrieve the description for this repository.
 
         Returns: String with the description of the repository
             as set by the user.
         """
         raise NotImplementedError(self.get_description)
 
     def set_description(self, description):
         """Set the description for this repository.
 
         Args:
           description: Text to set as description for this repository.
         """
         raise NotImplementedError(self.set_description)
 
     def get_config_stack(self) -> "StackedConfig":
         """Return a config stack for this repository.
 
         This stack accesses the configuration for both this repository
         itself (.git/config) and the global configuration, which usually
         lives in ~/.gitconfig.
 
         Returns: `Config` instance for this repository
         """
         from dulwich.config import StackedConfig
 
         backends = [self.get_config()] + StackedConfig.default_backends()
         return StackedConfig(backends, writable=backends[0])
 
     def get_shallow(self):
         """Get the set of shallow commits.
 
         Returns: Set of shallow commits.
         """
         f = self.get_named_file("shallow")
         if f is None:
             return set()
         with f:
             return {line.strip() for line in f}
 
     def update_shallow(self, new_shallow, new_unshallow):
         """Update the list of shallow objects.
 
         Args:
           new_shallow: Newly shallow objects
           new_unshallow: Newly no longer shallow objects
         """
         shallow = self.get_shallow()
         if new_shallow:
             shallow.update(new_shallow)
         if new_unshallow:
             shallow.difference_update(new_unshallow)
         if shallow:
             self._put_named_file(
                 "shallow", b"".join([sha + b"\n" for sha in shallow])
             )
         else:
             self._del_named_file("shallow")
 
     def get_peeled(self, ref):
         """Get the peeled value of a ref.
 
         Args:
           ref: The refname to peel.
         Returns: The fully-peeled SHA1 of a tag object, after peeling all
             intermediate tags; if the original ref does not point to a tag,
             this will equal the original SHA1.
         """
         cached = self.refs.get_peeled(ref)
         if cached is not None:
             return cached
         return self.object_store.peel_sha(self.refs[ref]).id
 
     def get_walker(self, include=None, *args, **kwargs):
         """Obtain a walker for this repository.
 
         Args:
           include: Iterable of SHAs of commits to include along with their
             ancestors. Defaults to [HEAD]
           exclude: Iterable of SHAs of commits to exclude along with their
             ancestors, overriding includes.
           order: ORDER_* constant specifying the order of results.
             Anything other than ORDER_DATE may result in O(n) memory usage.
           reverse: If True, reverse the order of output, requiring O(n)
             memory.
           max_entries: The maximum number of entries to yield, or None for
             no limit.
           paths: Iterable of file or subtree paths to show entries for.
           rename_detector: diff.RenameDetector object for detecting
             renames.
           follow: If True, follow path across renames/copies. Forces a
             default rename_detector.
           since: Timestamp to list commits after.
           until: Timestamp to list commits before.
           queue_cls: A class to use for a queue of commits, supporting the
             iterator protocol. The constructor takes a single argument, the
             Walker.
         Returns: A `Walker` object
         """
         from dulwich.walk import Walker
 
         if include is None:
             include = [self.head()]
         if isinstance(include, str):
             include = [include]
 
         kwargs["get_parents"] = lambda commit: self.get_parents(commit.id, commit)
 
         return Walker(self.object_store, include, *args, **kwargs)
 
     def __getitem__(self, name):
         """Retrieve a Git object by SHA1 or ref.
 
         Args:
           name: A Git object SHA1 or a ref name
         Returns: A `ShaFile` object, such as a Commit or Blob
         Raises:
           KeyError: when the specified ref or object does not exist
         """
         if not isinstance(name, bytes):
             raise TypeError(
                 "'name' must be bytestring, not %.80s" % type(name).__name__
             )
         if len(name) in (20, 40):
             try:
                 return self.object_store[name]
             except (KeyError, ValueError):
                 pass
         try:
             return self.object_store[self.refs[name]]
         except RefFormatError:
             raise KeyError(name)
 
     def __contains__(self, name: bytes) -> bool:
         """Check if a specific Git object or ref is present.
 
         Args:
           name: Git object SHA1 or ref name
         """
         if len(name) == 20 or (len(name) == 40 and valid_hexsha(name)):
             return name in self.object_store or name in self.refs
         else:
             return name in self.refs
 
     def __setitem__(self, name: bytes, value: Union[ShaFile, bytes]):
         """Set a ref.
 
         Args:
           name: ref name
           value: Ref value - either a ShaFile object, or a hex sha
         """
         if name.startswith(b"refs/") or name == b"HEAD":
             if isinstance(value, ShaFile):
                 self.refs[name] = value.id
             elif isinstance(value, bytes):
                 self.refs[name] = value
             else:
                 raise TypeError(value)
         else:
             raise ValueError(name)
 
     def __delitem__(self, name: bytes):
         """Remove a ref.
 
         Args:
           name: Name of the ref to remove
         """
         if name.startswith(b"refs/") or name == b"HEAD":
             del self.refs[name]
         else:
             raise ValueError(name)
 
     def _get_user_identity(self, config: "StackedConfig", kind: str = None) -> bytes:
         """Determine the identity to use for new commits."""
         # TODO(jelmer): Deprecate this function in favor of get_user_identity
         return get_user_identity(config)
 
     def _add_graftpoints(self, updated_graftpoints: Dict[bytes, List[bytes]]):
         """Add or modify graftpoints
 
         Args:
           updated_graftpoints: Dict of commit shas to list of parent shas
         """
 
         # Simple validation
         for commit, parents in updated_graftpoints.items():
             for sha in [commit] + parents:
                 check_hexsha(sha, "Invalid graftpoint")
 
         self._graftpoints.update(updated_graftpoints)
 
     def _remove_graftpoints(self, to_remove: List[bytes] = []) -> None:
         """Remove graftpoints
 
         Args:
           to_remove: List of commit shas
         """
         for sha in to_remove:
             del self._graftpoints[sha]
 
     def _read_heads(self, name):
         f = self.get_named_file(name)
         if f is None:
             return []
         with f:
             return [line.strip() for line in f.readlines() if line.strip()]
 
     def do_commit(  # noqa: C901
         self,
         message=None,
         committer=None,
         author=None,
         commit_timestamp=None,
         commit_timezone=None,
         author_timestamp=None,
         author_timezone=None,
         tree=None,
         encoding=None,
         ref=b"HEAD",
         merge_heads=None,
         no_verify=False,
     ):
         """Create a new commit.
 
         If not specified, `committer` and `author` default to
         get_user_identity(..., 'COMMITTER')
         and get_user_identity(..., 'AUTHOR') respectively.
 
         Args:
           message: Commit message
           committer: Committer fullname
           author: Author fullname
           commit_timestamp: Commit timestamp (defaults to now)
           commit_timezone: Commit timestamp timezone (defaults to GMT)
           author_timestamp: Author timestamp (defaults to commit
             timestamp)
           author_timezone: Author timestamp timezone
             (defaults to commit timestamp timezone)
           tree: SHA1 of the tree root to use (if not specified the
             current index will be committed).
           encoding: Encoding
           ref: Optional ref to commit to (defaults to current branch)
           merge_heads: Merge heads (defaults to .git/MERGE_HEAD)
           no_verify: Skip pre-commit and commit-msg hooks
 
         Returns:
           New commit SHA1
         """
 
         try:
             if not no_verify:
                 self.hooks["pre-commit"].execute()
         except HookError as e:
             raise CommitError(e)
         except KeyError:  # no hook defined, silent fallthrough
             pass
 
         c = Commit()
         if tree is None:
             index = self.open_index()
             c.tree = index.commit(self.object_store)
         else:
             if len(tree) != 40:
                 raise ValueError("tree must be a 40-byte hex sha string")
             c.tree = tree
 
         config = self.get_config_stack()
         if merge_heads is None:
             merge_heads = self._read_heads("MERGE_HEAD")
         if committer is None:
             committer = get_user_identity(config, kind="COMMITTER")
         check_user_identity(committer)
         c.committer = committer
         if commit_timestamp is None:
             # FIXME: Support GIT_COMMITTER_DATE environment variable
             commit_timestamp = time.time()
         c.commit_time = int(commit_timestamp)
         if commit_timezone is None:
             # FIXME: Use current user timezone rather than UTC
             commit_timezone = 0
         c.commit_timezone = commit_timezone
         if author is None:
             author = get_user_identity(config, kind="AUTHOR")
         c.author = author
         check_user_identity(author)
         if author_timestamp is None:
             # FIXME: Support GIT_AUTHOR_DATE environment variable
             author_timestamp = commit_timestamp
         c.author_time = int(author_timestamp)
         if author_timezone is None:
             author_timezone = commit_timezone
         c.author_timezone = author_timezone
         if encoding is None:
             try:
                 encoding = config.get(("i18n",), "commitEncoding")
             except KeyError:
                 pass  # No dice
         if encoding is not None:
             c.encoding = encoding
         if message is None:
             # FIXME: Try to read commit message from .git/MERGE_MSG
             raise ValueError("No commit message specified")
 
         try:
             if no_verify:
                 c.message = message
             else:
                 c.message = self.hooks["commit-msg"].execute(message)
                 if c.message is None:
                     c.message = message
         except HookError as e:
             raise CommitError(e)
         except KeyError:  # no hook defined, message not modified
             c.message = message
 
         if ref is None:
             # Create a dangling commit
             c.parents = merge_heads
             self.object_store.add_object(c)
         else:
             try:
                 old_head = self.refs[ref]
                 c.parents = [old_head] + merge_heads
                 self.object_store.add_object(c)
                 ok = self.refs.set_if_equals(
                     ref,
                     old_head,
                     c.id,
                     message=b"commit: " + message,
                     committer=committer,
                     timestamp=commit_timestamp,
                     timezone=commit_timezone,
                 )
             except KeyError:
                 c.parents = merge_heads
                 self.object_store.add_object(c)
                 ok = self.refs.add_if_new(
                     ref,
                     c.id,
                     message=b"commit: " + message,
                     committer=committer,
                     timestamp=commit_timestamp,
                     timezone=commit_timezone,
                 )
             if not ok:
                 # Fail if the atomic compare-and-swap failed, leaving the
                 # commit and all its objects as garbage.
                 raise CommitError("%s changed during commit" % (ref,))
 
         self._del_named_file("MERGE_HEAD")
 
         try:
             self.hooks["post-commit"].execute()
         except HookError as e:  # silent failure
             warnings.warn("post-commit hook failed: %s" % e, UserWarning)
         except KeyError:  # no hook defined, silent fallthrough
             pass
 
         return c.id
 
 
 def read_gitfile(f):
     """Read a ``.git`` file.
 
     The first line of the file should start with "gitdir: "
 
     Args:
       f: File-like object to read from
     Returns: A path
     """
     cs = f.read()
     if not cs.startswith("gitdir: "):
         raise ValueError("Expected file to start with 'gitdir: '")
     return cs[len("gitdir: ") :].rstrip("\n")
 
 
 class UnsupportedVersion(Exception):
     """Unsupported repository version."""
 
     def __init__(self, version):
         self.version = version
 
 
 class Repo(BaseRepo):
     """A git repository backed by local disk.
 
     To open an existing repository, call the contructor with
     the path of the repository.
 
     To create a new repository, use the Repo.init class method.
     """
 
     def __init__(self, root, object_store=None, bare=None):
         hidden_path = os.path.join(root, CONTROLDIR)
         if bare is None:
             if (os.path.isfile(hidden_path) or
                     os.path.isdir(os.path.join(hidden_path, OBJECTDIR))):
                 bare = False
             elif (os.path.isdir(os.path.join(root, OBJECTDIR)) and
                     os.path.isdir(os.path.join(root, REFSDIR))):
                 bare = True
             else:
                 raise NotGitRepository(
                     "No git repository was found at %(path)s" % dict(path=root)
                 )
 
         self.bare = bare
         if bare is False:
             if os.path.isfile(hidden_path):
                 with open(hidden_path, "r") as f:
                     path = read_gitfile(f)
                 self._controldir = os.path.join(root, path)
             else:
                 self._controldir = hidden_path
         else:
             self._controldir = root
         commondir = self.get_named_file(COMMONDIR)
         if commondir is not None:
             with commondir:
                 self._commondir = os.path.join(
                     self.controldir(),
                     os.fsdecode(commondir.read().rstrip(b"\r\n")),
                 )
         else:
             self._commondir = self._controldir
         self.path = root
         config = self.get_config()
         try:
             format_version = int(config.get("core", "repositoryformatversion"))
         except KeyError:
             format_version = 0
         if format_version != 0:
             raise UnsupportedVersion(format_version)
         if object_store is None:
             object_store = DiskObjectStore.from_config(
                 os.path.join(self.commondir(), OBJECTDIR), config
             )
         refs = DiskRefsContainer(
             self.commondir(), self._controldir, logger=self._write_reflog
         )
         BaseRepo.__init__(self, object_store, refs)
 
         self._graftpoints = {}
         graft_file = self.get_named_file(
             os.path.join("info", "grafts"), basedir=self.commondir()
         )
         if graft_file:
             with graft_file:
                 self._graftpoints.update(parse_graftpoints(graft_file))
         graft_file = self.get_named_file("shallow", basedir=self.commondir())
         if graft_file:
             with graft_file:
                 self._graftpoints.update(parse_graftpoints(graft_file))
 
         self.hooks["pre-commit"] = PreCommitShellHook(self.path, self.controldir())
         self.hooks["commit-msg"] = CommitMsgShellHook(self.controldir())
         self.hooks["post-commit"] = PostCommitShellHook(self.controldir())
         self.hooks["post-receive"] = PostReceiveShellHook(self.controldir())
 
     def _write_reflog(
         self, ref, old_sha, new_sha, committer, timestamp, timezone, message
     ):
         from .reflog import format_reflog_line
 
         path = os.path.join(self.controldir(), "logs", os.fsdecode(ref))
         try:
             os.makedirs(os.path.dirname(path))
         except FileExistsError:
             pass
         if committer is None:
             config = self.get_config_stack()
             committer = self._get_user_identity(config)
         check_user_identity(committer)
         if timestamp is None:
             timestamp = int(time.time())
         if timezone is None:
             timezone = 0  # FIXME
         with open(path, "ab") as f:
             f.write(
                 format_reflog_line(
                     old_sha, new_sha, committer, timestamp, timezone, message
                 )
                 + b"\n"
             )
 
     @classmethod
     def discover(cls, start="."):
         """Iterate parent directories to discover a repository
 
         Return a Repo object for the first parent directory that looks like a
         Git repository.
 
         Args:
           start: The directory to start discovery from (defaults to '.')
         """
         remaining = True
         path = os.path.abspath(start)
         while remaining:
             try:
                 return cls(path)
             except NotGitRepository:
                 path, remaining = os.path.split(path)
         raise NotGitRepository(
             "No git repository was found at %(path)s" % dict(path=start)
         )
 
     def controldir(self):
         """Return the path of the control directory."""
         return self._controldir
 
     def commondir(self):
         """Return the path of the common directory.
 
         For a main working tree, it is identical to controldir().
 
         For a linked working tree, it is the control directory of the
         main working tree."""
 
         return self._commondir
 
     def _determine_file_mode(self):
         """Probe the file-system to determine whether permissions can be trusted.
 
         Returns: True if permissions can be trusted, False otherwise.
         """
         fname = os.path.join(self.path, ".probe-permissions")
         with open(fname, "w") as f:
             f.write("")
 
         st1 = os.lstat(fname)
         try:
             os.chmod(fname, st1.st_mode ^ stat.S_IXUSR)
         except PermissionError:
             return False
         st2 = os.lstat(fname)
 
         os.unlink(fname)
 
         mode_differs = st1.st_mode != st2.st_mode
         st2_has_exec = (st2.st_mode & stat.S_IXUSR) != 0
 
         return mode_differs and st2_has_exec
 
     def _put_named_file(self, path, contents):
         """Write a file to the control dir with the given name and contents.
 
         Args:
           path: The path to the file, relative to the control dir.
           contents: A string to write to the file.
         """
         path = path.lstrip(os.path.sep)
         with GitFile(os.path.join(self.controldir(), path), "wb") as f:
             f.write(contents)
 
     def _del_named_file(self, path):
         try:
             os.unlink(os.path.join(self.controldir(), path))
         except FileNotFoundError:
             return
 
     def get_named_file(self, path, basedir=None):
         """Get a file from the control dir with a specific name.
 
         Although the filename should be interpreted as a filename relative to
         the control dir in a disk-based Repo, the object returned need not be
         pointing to a file in that location.
 
         Args:
           path: The path to the file, relative to the control dir.
           basedir: Optional argument that specifies an alternative to the
             control dir.
         Returns: An open file object, or None if the file does not exist.
         """
         # TODO(dborowitz): sanitize filenames, since this is used directly by
         # the dumb web serving code.
         if basedir is None:
             basedir = self.controldir()
         path = path.lstrip(os.path.sep)
         try:
             return open(os.path.join(basedir, path), "rb")
         except FileNotFoundError:
             return None
 
     def index_path(self):
         """Return path to the index file."""
         return os.path.join(self.controldir(), INDEX_FILENAME)
 
     def open_index(self) -> "Index":
         """Open the index for this repository.
 
         Raises:
           NoIndexPresent: If no index is present
         Returns: The matching `Index`
         """
         from dulwich.index import Index
 
         if not self.has_index():
             raise NoIndexPresent()
         return Index(self.index_path())
 
     def has_index(self):
         """Check if an index is present."""
         # Bare repos must never have index files; non-bare repos may have a
         # missing index file, which is treated as empty.
         return not self.bare
 
     def stage(self, fs_paths: Union[str, bytes, os.PathLike, Iterable[Union[str, bytes, os.PathLike]]]) -> None:
         """Stage a set of paths.
 
         Args:
           fs_paths: List of paths, relative to the repository path
         """
 
         root_path_bytes = os.fsencode(self.path)
 
         if isinstance(fs_paths, (str, bytes, os.PathLike)):
             fs_paths = [fs_paths]
         fs_paths = list(fs_paths)
 
         from dulwich.index import (
             blob_from_path_and_stat,
             index_entry_from_stat,
             _fs_to_tree_path,
         )
 
         index = self.open_index()
         blob_normalizer = self.get_blob_normalizer()
         for fs_path in fs_paths:
             if not isinstance(fs_path, bytes):
                 fs_path = os.fsencode(fs_path)
             if os.path.isabs(fs_path):
                 raise ValueError(
                     "path %r should be relative to "
                     "repository root, not absolute" % fs_path
                 )
             tree_path = _fs_to_tree_path(fs_path)
             full_path = os.path.join(root_path_bytes, fs_path)
             try:
                 st = os.lstat(full_path)
             except OSError:
                 # File no longer exists
                 try:
                     del index[tree_path]
                 except KeyError:
                     pass  # already removed
             else:
                 if not stat.S_ISREG(st.st_mode) and not stat.S_ISLNK(st.st_mode):
                     try:
                         del index[tree_path]
                     except KeyError:
                         pass
                 else:
                     blob = blob_from_path_and_stat(full_path, st)
                     blob = blob_normalizer.checkin_normalize(blob, fs_path)
                     self.object_store.add_object(blob)
                     index[tree_path] = index_entry_from_stat(st, blob.id, 0)
         index.write()
 
     def unstage(self, fs_paths: List[str]):
         """unstage specific file in the index
         Args:
           fs_paths: a list of files to unstage,
             relative to the repository path
         """
         from dulwich.index import (
             IndexEntry,
             _fs_to_tree_path,
             )
 
         index = self.open_index()
         try:
             tree_id = self[b'HEAD'].tree
         except KeyError:
             # no head mean no commit in the repo
             for fs_path in fs_paths:
                 tree_path = _fs_to_tree_path(fs_path)
                 del index[tree_path]
             index.write()
             return
 
         for fs_path in fs_paths:
             tree_path = _fs_to_tree_path(fs_path)
             try:
                 tree_entry = self.object_store[tree_id].lookup_path(
                     self.object_store.__getitem__, tree_path)
             except KeyError:
                 # if tree_entry didnt exist, this file was being added, so
                 # remove index entry
                 try:
                     del index[tree_path]
                     continue
                 except KeyError:
                     raise KeyError("file '%s' not in index" % (tree_path.decode()))
 
             st = None
             try:
                 st = os.lstat(os.path.join(self.path, fs_path))
             except FileNotFoundError:
                 pass
 
             index_entry = IndexEntry(
                 ctime=(self[b'HEAD'].commit_time, 0),
                 mtime=(self[b'HEAD'].commit_time, 0),
                 dev=st.st_dev if st else 0,
                 ino=st.st_ino if st else 0,
                 mode=tree_entry[0],
                 uid=st.st_uid if st else 0,
                 gid=st.st_gid if st else 0,
                 size=len(self[tree_entry[1]].data),
                 sha=tree_entry[1],
                 flags=0,
                 extended_flags=0
             )
 
             index[tree_path] = index_entry
         index.write()
 
     def clone(
         self,
         target_path,
         mkdir=True,
         bare=False,
         origin=b"origin",
         checkout=None,
     ):
         """Clone this repository.
 
         Args:
           target_path: Target path
           mkdir: Create the target directory
           bare: Whether to create a bare repository
           origin: Base name for refs in target repository
             cloned from this repository
         Returns: Created repository as `Repo`
         """
         if not bare:
             target = self.init(target_path, mkdir=mkdir)
         else:
             if checkout:
                 raise ValueError("checkout and bare are incompatible")
             target = self.init_bare(target_path, mkdir=mkdir)
         self.fetch(target)
         encoded_path = self.path
         if not isinstance(encoded_path, bytes):
             encoded_path = os.fsencode(encoded_path)
         ref_message = b"clone: from " + encoded_path
         target.refs.import_refs(
             b"refs/remotes/" + origin,
             self.refs.as_dict(b"refs/heads"),
             message=ref_message,
         )
         target.refs.import_refs(
             b"refs/tags", self.refs.as_dict(b"refs/tags"), message=ref_message
         )
         try:
             target.refs.add_if_new(
                 DEFAULT_REF, self.refs[DEFAULT_REF], message=ref_message
             )
         except KeyError:
             pass
         target_config = target.get_config()
         target_config.set(("remote", "origin"), "url", encoded_path)
         target_config.set(
             ("remote", "origin"),
             "fetch",
             "+refs/heads/*:refs/remotes/origin/*",
         )
         target_config.write_to_path()
 
         # Update target head
         head_chain, head_sha = self.refs.follow(b"HEAD")
         if head_chain and head_sha is not None:
             target.refs.set_symbolic_ref(b"HEAD", head_chain[-1], message=ref_message)
             target[b"HEAD"] = head_sha
 
             if checkout is None:
                 checkout = not bare
             if checkout:
                 # Checkout HEAD to target dir
                 target.reset_index()
 
         return target
 
     def reset_index(self, tree=None):
         """Reset the index back to a specific tree.
 
         Args:
           tree: Tree SHA to reset to, None for current HEAD tree.
         """
         from dulwich.index import (
             build_index_from_tree,
             validate_path_element_default,
             validate_path_element_ntfs,
         )
 
         if tree is None:
             tree = self[b"HEAD"].tree
         config = self.get_config()
         honor_filemode = config.get_boolean(b"core", b"filemode", os.name != "nt")
         if config.get_boolean(b"core", b"core.protectNTFS", os.name == "nt"):
             validate_path_element = validate_path_element_ntfs
         else:
             validate_path_element = validate_path_element_default
         return build_index_from_tree(
             self.path,
             self.index_path(),
             self.object_store,
             tree,
             honor_filemode=honor_filemode,
             validate_path_element=validate_path_element,
         )
 
     def get_config(self) -> "ConfigFile":
         """Retrieve the config object.
 
         Returns: `ConfigFile` object for the ``.git/config`` file.
         """
         from dulwich.config import ConfigFile
 
         path = os.path.join(self._controldir, "config")
         try:
             return ConfigFile.from_path(path)
         except FileNotFoundError:
             ret = ConfigFile()
             ret.path = path
             return ret
 
     def get_description(self):
         """Retrieve the description of this repository.
 
         Returns: A string describing the repository or None.
         """
         path = os.path.join(self._controldir, "description")
         try:
             with GitFile(path, "rb") as f:
                 return f.read()
         except FileNotFoundError:
             return None
 
     def __repr__(self):
         return "<Repo at %r>" % self.path
 
     def set_description(self, description):
         """Set the description for this repository.
 
         Args:
           description: Text to set as description for this repository.
         """
 
         self._put_named_file("description", description)
 
     @classmethod
     def _init_maybe_bare(cls, path, controldir, bare, object_store=None):
         for d in BASE_DIRECTORIES:
             os.mkdir(os.path.join(controldir, *d))
         if object_store is None:
             object_store = DiskObjectStore.init(os.path.join(controldir, OBJECTDIR))
         ret = cls(path, bare=bare, object_store=object_store)
         ret.refs.set_symbolic_ref(b"HEAD", DEFAULT_REF)
         ret._init_files(bare)
         return ret
 
     @classmethod
     def init(cls, path, mkdir=False):
         """Create a new repository.
 
         Args:
           path: Path in which to create the repository
           mkdir: Whether to create the directory
         Returns: `Repo` instance
         """
         if mkdir:
             os.mkdir(path)
         controldir = os.path.join(path, CONTROLDIR)
         os.mkdir(controldir)
         _set_filesystem_hidden(controldir)
         return cls._init_maybe_bare(path, controldir, False)
 
     @classmethod
     def _init_new_working_directory(cls, path, main_repo, identifier=None, mkdir=False):
         """Create a new working directory linked to a repository.
 
         Args:
           path: Path in which to create the working tree.
           main_repo: Main repository to reference
           identifier: Worktree identifier
           mkdir: Whether to create the directory
         Returns: `Repo` instance
         """
         if mkdir:
             os.mkdir(path)
         if identifier is None:
             identifier = os.path.basename(path)
         main_worktreesdir = os.path.join(main_repo.controldir(), WORKTREES)
         worktree_controldir = os.path.join(main_worktreesdir, identifier)
         gitdirfile = os.path.join(path, CONTROLDIR)
         with open(gitdirfile, "wb") as f:
             f.write(b"gitdir: " + os.fsencode(worktree_controldir) + b"\n")
         try:
             os.mkdir(main_worktreesdir)
         except FileExistsError:
             pass
         try:
             os.mkdir(worktree_controldir)
         except FileExistsError:
             pass
         with open(os.path.join(worktree_controldir, GITDIR), "wb") as f:
             f.write(os.fsencode(gitdirfile) + b"\n")
         with open(os.path.join(worktree_controldir, COMMONDIR), "wb") as f:
             f.write(b"../..\n")
         with open(os.path.join(worktree_controldir, "HEAD"), "wb") as f:
             f.write(main_repo.head() + b"\n")
         r = cls(path)
         r.reset_index()
         return r
 
     @classmethod
     def init_bare(cls, path, mkdir=False, object_store=None):
         """Create a new bare repository.
 
         ``path`` should already exist and be an empty directory.
 
         Args:
           path: Path to create bare repository in
         Returns: a `Repo` instance
         """
         if mkdir:
             os.mkdir(path)
         return cls._init_maybe_bare(path, path, True, object_store=object_store)
 
     create = init_bare
 
     def close(self):
         """Close any files opened by this repository."""
         self.object_store.close()
 
     def __enter__(self):
         return self
 
     def __exit__(self, exc_type, exc_val, exc_tb):
         self.close()
 
     def get_blob_normalizer(self):
         """Return a BlobNormalizer object"""
         # TODO Parse the git attributes files
         git_attributes = {}
         config_stack = self.get_config_stack()
         try:
             tree = self.object_store[self.refs[b"HEAD"]].tree
             return TreeBlobNormalizer(
                 config_stack,
                 git_attributes,
                 self.object_store,
                 tree,
             )
         except KeyError:
             return BlobNormalizer(config_stack, git_attributes)
 
 
 class MemoryRepo(BaseRepo):
     """Repo that stores refs, objects, and named files in memory.
 
     MemoryRepos are always bare: they have no working tree and no index, since
     those have a stronger dependency on the filesystem.
     """
 
     def __init__(self):
         from dulwich.config import ConfigFile
 
         self._reflog = []
         refs_container = DictRefsContainer({}, logger=self._append_reflog)
         BaseRepo.__init__(self, MemoryObjectStore(), refs_container)
         self._named_files = {}
         self.bare = True
         self._config = ConfigFile()
         self._description = None
 
     def _append_reflog(self, *args):
         self._reflog.append(args)
 
     def set_description(self, description):
         self._description = description
 
     def get_description(self):
         return self._description
 
     def _determine_file_mode(self):
         """Probe the file-system to determine whether permissions can be trusted.
 
         Returns: True if permissions can be trusted, False otherwise.
         """
         return sys.platform != "win32"
 
     def _put_named_file(self, path, contents):
         """Write a file to the control dir with the given name and contents.
 
         Args:
           path: The path to the file, relative to the control dir.
           contents: A string to write to the file.
         """
         self._named_files[path] = contents
 
     def _del_named_file(self, path):
         try:
             del self._named_files[path]
         except KeyError:
             pass
 
     def get_named_file(self, path, basedir=None):
         """Get a file from the control dir with a specific name.
 
         Although the filename should be interpreted as a filename relative to
         the control dir in a disk-baked Repo, the object returned need not be
         pointing to a file in that location.
 
         Args:
           path: The path to the file, relative to the control dir.
         Returns: An open file object, or None if the file does not exist.
         """
         contents = self._named_files.get(path, None)
         if contents is None:
             return None
         return BytesIO(contents)
 
     def open_index(self):
         """Fail to open index for this repo, since it is bare.
 
         Raises:
           NoIndexPresent: Raised when no index is present
         """
         raise NoIndexPresent()
 
     def get_config(self):
         """Retrieve the config object.
 
         Returns: `ConfigFile` object.
         """
         return self._config
 
     @classmethod
     def init_bare(cls, objects, refs):
         """Create a new bare repository in memory.
 
         Args:
           objects: Objects for the new repository,
             as iterable
           refs: Refs as dictionary, mapping names
             to object SHA1s
         """
         ret = cls()
         for obj in objects:
             ret.object_store.add_object(obj)
         for refname, sha in refs.items():
             ret.refs.add_if_new(refname, sha)
         ret._init_files(bare=True)
         return ret