diff --git a/swh/storage/tests/storage_data.py b/swh/storage/tests/storage_data.py
index 0811da27..79600885 100644
--- a/swh/storage/tests/storage_data.py
+++ b/swh/storage/tests/storage_data.py
@@ -1,522 +1,523 @@
 # Copyright (C) 2015-2019  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import datetime
 from swh.model.hashutil import hash_to_bytes
 from swh.model import from_disk
 
 
 class StorageData:
     def __getattr__(self, key):
         try:
             v = globals()[key]
         except KeyError as e:
             raise AttributeError(e.args[0])
         if hasattr(v, "copy"):
             return v.copy()
         return v
 
 
 data = StorageData()
 
 
 cont = {
     "data": b"42\n",
     "length": 3,
     "sha1": hash_to_bytes("34973274ccef6ab4dfaaf86599792fa9c3fe4689"),
     "sha1_git": hash_to_bytes("d81cc0710eb6cf9efd5b920a8453e1e07157b6cd"),
     "sha256": hash_to_bytes(
         "673650f936cb3b0a2f93ce09d81be10748b1b203c19e8176b4eefc1964a0cf3a"
     ),
     "blake2s256": hash_to_bytes(
         "d5fe1939576527e42cfd76a9455a2432fe7f56669564577dd93c4280e76d661d"
     ),
     "status": "visible",
 }
 
 cont2 = {
     "data": b"4242\n",
     "length": 5,
     "sha1": hash_to_bytes("61c2b3a30496d329e21af70dd2d7e097046d07b7"),
     "sha1_git": hash_to_bytes("36fade77193cb6d2bd826161a0979d64c28ab4fa"),
     "sha256": hash_to_bytes(
         "859f0b154fdb2d630f45e1ecae4a862915435e663248bb8461d914696fc047cd"
     ),
     "blake2s256": hash_to_bytes(
         "849c20fad132b7c2d62c15de310adfe87be94a379941bed295e8141c6219810d"
     ),
     "status": "visible",
 }
 
 cont3 = {
     "data": b"424242\n",
     "length": 7,
     "sha1": hash_to_bytes("3e21cc4942a4234c9e5edd8a9cacd1670fe59f13"),
     "sha1_git": hash_to_bytes("c932c7649c6dfa4b82327d121215116909eb3bea"),
     "sha256": hash_to_bytes(
         "92fb72daf8c6818288a35137b72155f507e5de8d892712ab96277aaed8cf8a36"
     ),
     "blake2s256": hash_to_bytes(
         "76d0346f44e5a27f6bafdd9c2befd304aff83780f93121d801ab6a1d4769db11"
     ),
     "status": "visible",
     "ctime": "2019-12-01 00:00:00Z",
 }
 
 contents = (cont, cont2, cont3)
 
 
 missing_cont = {
     "data": b"missing\n",
     "length": 8,
     "sha1": hash_to_bytes("f9c24e2abb82063a3ba2c44efd2d3c797f28ac90"),
     "sha1_git": hash_to_bytes("33e45d56f88993aae6a0198013efa80716fd8919"),
     "sha256": hash_to_bytes(
         "6bbd052ab054ef222c1c87be60cd191addedd24cc882d1f5f7f7be61dc61bb3a"
     ),
     "blake2s256": hash_to_bytes(
         "306856b8fd879edb7b6f1aeaaf8db9bbecc993cd7f776c333ac3a782fa5c6eba"
     ),
     "status": "absent",
 }
 
 skipped_cont = {
     "length": 1024 * 1024 * 200,
     "sha1_git": hash_to_bytes("33e45d56f88993aae6a0198013efa80716fd8920"),
     "sha1": hash_to_bytes("43e45d56f88993aae6a0198013efa80716fd8920"),
     "sha256": hash_to_bytes(
         "7bbd052ab054ef222c1c87be60cd191addedd24cc882d1f5f7f7be61dc61bb3a"
     ),
     "blake2s256": hash_to_bytes(
         "ade18b1adecb33f891ca36664da676e12c772cc193778aac9a137b8dc5834b9b"
     ),
     "reason": "Content too long",
     "status": "absent",
     "origin": "file:///dev/zero",
 }
 
 skipped_cont2 = {
     "length": 1024 * 1024 * 300,
     "sha1_git": hash_to_bytes("44e45d56f88993aae6a0198013efa80716fd8921"),
     "sha1": hash_to_bytes("54e45d56f88993aae6a0198013efa80716fd8920"),
     "sha256": hash_to_bytes(
         "8cbd052ab054ef222c1c87be60cd191addedd24cc882d1f5f7f7be61dc61bb3a"
     ),
     "blake2s256": hash_to_bytes(
         "9ce18b1adecb33f891ca36664da676e12c772cc193778aac9a137b8dc5834b9b"
     ),
     "reason": "Content too long",
     "status": "absent",
 }
 
 dir = {
     "id": hash_to_bytes("340133423253310030f531e632a733ff37c3a930"),
     "entries": (
         {
             "name": b"foo",
             "type": "file",
             "target": hash_to_bytes("d81cc0710eb6cf9efd5b920a8453e1e07157b6cd"),  # cont
             "perms": from_disk.DentryPerms.content,
         },
         {
             "name": b"bar\xc3",
             "type": "dir",
             "target": b"12345678901234567890",
             "perms": from_disk.DentryPerms.directory,
         },
     ),
 }
 
 dir2 = {
     "id": hash_to_bytes("340133423253310030f531e632a733ff37c3a935"),
     "entries": (
         {
             "name": b"oof",
             "type": "file",
             "target": hash_to_bytes(  # cont2
                 "36fade77193cb6d2bd826161a0979d64c28ab4fa"
             ),
             "perms": from_disk.DentryPerms.content,
         },
     ),
 }
 
 dir3 = {
     "id": hash_to_bytes("33e45d56f88993aae6a0198013efa80716fd8921"),
     "entries": (
         {
             "name": b"foo",
             "type": "file",
             "target": hash_to_bytes("d81cc0710eb6cf9efd5b920a8453e1e07157b6cd"),  # cont
             "perms": from_disk.DentryPerms.content,
         },
         {
             "name": b"subdir",
             "type": "dir",
             "target": hash_to_bytes("340133423253310030f531e632a733ff37c3a930"),  # dir
             "perms": from_disk.DentryPerms.directory,
         },
         {
             "name": b"hello",
             "type": "file",
             "target": b"12345678901234567890",
             "perms": from_disk.DentryPerms.content,
         },
     ),
 }
 
 dir4 = {
     "id": hash_to_bytes("33e45d56f88993aae6a0198013efa80716fd8922"),
     "entries": (
         {
             "name": b"subdir1",
             "type": "dir",
             "target": hash_to_bytes("33e45d56f88993aae6a0198013efa80716fd8921"),  # dir3
             "perms": from_disk.DentryPerms.directory,
         },
     ),
 }
 
 dierctories = (dir, dir2, dir3, dir4)
 
 
 minus_offset = datetime.timezone(datetime.timedelta(minutes=-120))
 plus_offset = datetime.timezone(datetime.timedelta(minutes=120))
 
 revision = {
     "id": b"56789012345678901234",
     "message": b"hello",
     "author": {
         "name": b"Nicolas Dandrimont",
         "email": b"nicolas@example.com",
         "fullname": b"Nicolas Dandrimont <nicolas@example.com> ",
     },
     "date": {
         "timestamp": {"seconds": 1234567890, "microseconds": 0},
         "offset": 120,
         "negative_utc": False,
     },
     "committer": {
         "name": b"St\xc3fano Zacchiroli",
         "email": b"stefano@example.com",
         "fullname": b"St\xc3fano Zacchiroli <stefano@example.com>",
     },
     "committer_date": {
         "timestamp": {"seconds": 1123456789, "microseconds": 0},
         "offset": 0,
         "negative_utc": True,
     },
     "parents": (b"01234567890123456789", b"23434512345123456789"),
     "type": "git",
     "directory": hash_to_bytes("340133423253310030f531e632a733ff37c3a930"),  # dir
     "metadata": {
         "checksums": {"sha1": "tarball-sha1", "sha256": "tarball-sha256",},
         "signed-off-by": "some-dude",
         "extra_headers": [
             ["gpgsig", b"test123"],
-            ["mergetags", [b"foo\\bar", b"\x22\xaf\x89\x80\x01\x00"]],
+            ["mergetag", b"foo\\bar"],
+            ["mergetag", b"\x22\xaf\x89\x80\x01\x00"],
         ],
     },
     "synthetic": True,
 }
 
 revision2 = {
     "id": b"87659012345678904321",
     "message": b"hello again",
     "author": {
         "name": b"Roberto Dicosmo",
         "email": b"roberto@example.com",
         "fullname": b"Roberto Dicosmo <roberto@example.com>",
     },
     "date": {
         "timestamp": {"seconds": 1234567843, "microseconds": 220000,},
         "offset": -720,
         "negative_utc": False,
     },
     "committer": {
         "name": b"tony",
         "email": b"ar@dumont.fr",
         "fullname": b"tony <ar@dumont.fr>",
     },
     "committer_date": {
         "timestamp": {"seconds": 1123456789, "microseconds": 0},
         "offset": 0,
         "negative_utc": False,
     },
     "parents": (b"01234567890123456789",),
     "type": "git",
     "directory": hash_to_bytes("340133423253310030f531e632a733ff37c3a935"),  # dir2
     "metadata": None,
     "synthetic": False,
 }
 
 revision3 = {
     "id": hash_to_bytes("7026b7c1a2af56521e951c01ed20f255fa054238"),
     "message": b"a simple revision with no parents this time",
     "author": {
         "name": b"Roberto Dicosmo",
         "email": b"roberto@example.com",
         "fullname": b"Roberto Dicosmo <roberto@example.com>",
     },
     "date": {
         "timestamp": {"seconds": 1234567843, "microseconds": 220000,},
         "offset": -720,
         "negative_utc": False,
     },
     "committer": {
         "name": b"tony",
         "email": b"ar@dumont.fr",
         "fullname": b"tony <ar@dumont.fr>",
     },
     "committer_date": {
         "timestamp": {"seconds": 1127351742, "microseconds": 0},
         "offset": 0,
         "negative_utc": False,
     },
     "parents": (),
     "type": "git",
     "directory": hash_to_bytes("340133423253310030f531e632a733ff37c3a935"),  # dir2
     "metadata": None,
     "synthetic": True,
 }
 
 revision4 = {
     "id": hash_to_bytes("368a48fe15b7db2383775f97c6b247011b3f14f4"),
     "message": b"parent of self.revision2",
     "author": {
         "name": b"me",
         "email": b"me@soft.heri",
         "fullname": b"me <me@soft.heri>",
     },
     "date": {
         "timestamp": {"seconds": 1244567843, "microseconds": 220000,},
         "offset": -720,
         "negative_utc": False,
     },
     "committer": {
         "name": b"committer-dude",
         "email": b"committer@dude.com",
         "fullname": b"committer-dude <committer@dude.com>",
     },
     "committer_date": {
         "timestamp": {"seconds": 1244567843, "microseconds": 220000,},
         "offset": -720,
         "negative_utc": False,
     },
     "parents": (
         hash_to_bytes("7026b7c1a2af56521e951c01ed20f255fa054238"),
     ),  # revision3
     "type": "git",
     "directory": hash_to_bytes("340133423253310030f531e632a733ff37c3a930"),  # dir
     "metadata": None,
     "synthetic": False,
 }
 
 revisions = (revision, revision2, revision3, revision4)
 
 
 origin = {
     "url": "file:///dev/null",
 }
 
 origin2 = {
     "url": "file:///dev/zero",
 }
 
 origins = (origin, origin2)
 
 
 metadata_authority = {
     "type": "deposit",
     "url": "http://hal.inria.example.com/",
     "metadata": {"location": "France"},
 }
 metadata_authority2 = {
     "type": "registry",
     "url": "http://wikidata.example.com/",
     "metadata": {},
 }
 
 metadata_fetcher = {
     "name": "swh-deposit",
     "version": "0.0.1",
     "metadata": {"sword_version": "2"},
 }
 metadata_fetcher2 = {
     "name": "swh-example",
     "version": "0.0.1",
     "metadata": {},
 }
 
 date_visit1 = datetime.datetime(2015, 1, 1, 23, 0, 0, tzinfo=datetime.timezone.utc)
 type_visit1 = "git"
 
 date_visit2 = datetime.datetime(2017, 1, 1, 23, 0, 0, tzinfo=datetime.timezone.utc)
 type_visit2 = "hg"
 
 date_visit3 = datetime.datetime(2018, 1, 1, 23, 0, 0, tzinfo=datetime.timezone.utc)
 type_visit3 = "deb"
 
 release = {
     "id": b"87659012345678901234",
     "name": b"v0.0.1",
     "author": {
         "name": b"olasd",
         "email": b"nic@olasd.fr",
         "fullname": b"olasd <nic@olasd.fr>",
     },
     "date": {
         "timestamp": {"seconds": 1234567890, "microseconds": 0},
         "offset": 42,
         "negative_utc": False,
     },
     "target": b"43210987654321098765",
     "target_type": "revision",
     "message": b"synthetic release",
     "synthetic": True,
 }
 
 release2 = {
     "id": b"56789012348765901234",
     "name": b"v0.0.2",
     "author": {
         "name": b"tony",
         "email": b"ar@dumont.fr",
         "fullname": b"tony <ar@dumont.fr>",
     },
     "date": {
         "timestamp": {"seconds": 1634366813, "microseconds": 0},
         "offset": -120,
         "negative_utc": False,
     },
     "target": b"432109\xa9765432\xc309\x00765",
     "target_type": "revision",
     "message": b"v0.0.2\nMisc performance improvements + bug fixes",
     "synthetic": False,
 }
 
 release3 = {
     "id": b"87659012345678904321",
     "name": b"v0.0.2",
     "author": {
         "name": b"tony",
         "email": b"tony@ardumont.fr",
         "fullname": b"tony <tony@ardumont.fr>",
     },
     "date": {
         "timestamp": {"seconds": 1634336813, "microseconds": 0},
         "offset": 0,
         "negative_utc": False,
     },
     "target": b"87659012345678904321",  # revision2
     "target_type": "revision",
     "message": b"yet another synthetic release",
     "synthetic": True,
 }
 
 releases = (release, release2, release3)
 
 
 snapshot = {
     "id": hash_to_bytes("2498dbf535f882bc7f9a18fb16c9ad27fda7bab7"),
     "branches": {
         b"master": {
             "target": b"56789012345678901234",  # revision
             "target_type": "revision",
         },
     },
 }
 
 empty_snapshot = {
     "id": hash_to_bytes("1a8893e6a86f444e8be8e7bda6cb34fb1735a00e"),
     "branches": {},
 }
 
 complete_snapshot = {
     "id": hash_to_bytes("6e65b86363953b780d92b0a928f3e8fcdd10db36"),
     "branches": {
         b"directory": {
             "target": hash_to_bytes("1bd0e65f7d2ff14ae994de17a1e7fe65111dcad8"),
             "target_type": "directory",
         },
         b"directory2": {
             "target": hash_to_bytes("1bd0e65f7d2ff14ae994de17a1e7fe65111dcad8"),
             "target_type": "directory",
         },
         b"content": {
             "target": hash_to_bytes("fe95a46679d128ff167b7c55df5d02356c5a1ae1"),
             "target_type": "content",
         },
         b"alias": {"target": b"revision", "target_type": "alias",},
         b"revision": {
             "target": hash_to_bytes("aafb16d69fd30ff58afdd69036a26047f3aebdc6"),
             "target_type": "revision",
         },
         b"release": {
             "target": hash_to_bytes("7045404f3d1c54e6473c71bbb716529fbad4be24"),
             "target_type": "release",
         },
         b"snapshot": {
             "target": hash_to_bytes("1a8893e6a86f444e8be8e7bda6cb34fb1735a00e"),
             "target_type": "snapshot",
         },
         b"dangling": None,
     },
 }
 
 origin_metadata = {
     "origin_url": origin["url"],
     "discovery_date": datetime.datetime(
         2015, 1, 1, 21, 0, 0, tzinfo=datetime.timezone.utc
     ),
     "authority": {
         "type": metadata_authority["type"],
         "url": metadata_authority["url"],
     },
     "fetcher": {
         "name": metadata_fetcher["name"],
         "version": metadata_fetcher["version"],
     },
     "format": "json",
     "metadata": b'{"foo": "bar"}',
 }
 origin_metadata2 = {
     "origin_url": origin["url"],
     "discovery_date": datetime.datetime(
         2017, 1, 1, 22, 0, 0, tzinfo=datetime.timezone.utc
     ),
     "authority": {
         "type": metadata_authority["type"],
         "url": metadata_authority["url"],
     },
     "fetcher": {
         "name": metadata_fetcher["name"],
         "version": metadata_fetcher["version"],
     },
     "format": "yaml",
     "metadata": b"foo: bar",
 }
 origin_metadata3 = {
     "origin_url": origin["url"],
     "discovery_date": datetime.datetime(
         2017, 1, 1, 22, 0, 0, tzinfo=datetime.timezone.utc
     ),
     "authority": {
         "type": metadata_authority2["type"],
         "url": metadata_authority2["url"],
     },
     "fetcher": {
         "name": metadata_fetcher2["name"],
         "version": metadata_fetcher2["version"],
     },
     "format": "yaml",
     "metadata": b"foo: bar",
 }
 
 person = {
     "name": b"John Doe",
     "email": b"john.doe@institute.org",
     "fullname": b"John Doe <john.doe@institute.org>",
 }