diff --git a/swh/loader/git/tests/test_from_disk.py b/swh/loader/git/tests/test_from_disk.py
--- a/swh/loader/git/tests/test_from_disk.py
+++ b/swh/loader/git/tests/test_from_disk.py
@@ -4,8 +4,8 @@
 # See top-level LICENSE file for more information
 
 import os.path
-import subprocess
 
+import dulwich.repo
 
 from swh.loader.git.from_disk import GitLoaderFromDisk as OrigGitLoaderFromDisk
 from swh.loader.git.from_disk import GitLoaderFromArchive as OrigGitLoaderFromArchive
@@ -132,6 +132,7 @@
             directory=self.destination_path,
         )
         self.storage = self.loader.storage
+        self.repo = dulwich.repo.Repo(self.destination_path)
 
     def load(self):
         return self.loader.load()
@@ -169,7 +170,7 @@
 
         self.assertContentsContain(CONTENT1)
         self.assertCountDirectories(7)
-        self.assertCountReleases(0)  # FIXME: why not 2?
+        self.assertCountReleases(0)  # FIXME: should be 2 after T2059
         self.assertCountRevisions(7)
         self.assertCountSnapshots(1)
 
@@ -207,17 +208,6 @@
     """Tests for the GitLoaderFromDisk. Includes the common ones, and
     add others that only work with a local dir."""
 
-    def _git(self, *cmd):
-        """Small wrapper around subprocess to call Git."""
-        try:
-            return subprocess.check_output(
-                ["git", "-C", self.destination_path] + list(cmd)
-            )
-        except subprocess.CalledProcessError as e:
-            print(e.output)
-            print(e.stderr)
-            raise
-
     def test_load_changed(self):
         """Loads a repository, makes some changes by adding files, commits,
         and merges, load it again, and check the storage contains everything
@@ -226,35 +216,31 @@
         res = self.load()
         self.assertEqual(res["status"], "eventful", res)
 
-        self._git("config", "--local", "user.email", "you@example.com")
-        self._git("config", "--local", "user.name", "Your Name")
-
         # Load with a new file + revision
         with open(os.path.join(self.destination_path, "hello.py"), "a") as fd:
             fd.write("print('Hello world')\n")
 
-        self._git("add", "hello.py")
-        self._git("commit", "-m", "Hello world")
-        new_revision = self._git("rev-parse", "master").decode().strip()
+        self.repo.stage([b"hello.py"])
+        new_revision = self.repo.do_commit(b"Hello world\n").decode()
+        new_dir = "85dae072a5aa9923ffa7a7568f819ff21bf49858"
+
+        assert self.repo[new_revision.encode()].tree == new_dir.encode()
 
         revisions = REVISIONS1.copy()
         assert new_revision not in revisions
-        revisions[new_revision] = "85dae072a5aa9923ffa7a7568f819ff21bf49858"
+        revisions[new_revision] = new_dir
 
         res = self.load()
         self.assertEqual(res["status"], "eventful")
 
         self.assertCountContents(4 + 1)
         self.assertCountDirectories(7 + 1)
-        self.assertCountReleases(0)  # FIXME: why not 2?
+        self.assertCountReleases(0)  # FIXME: should be 2 after T2059
         self.assertCountRevisions(7 + 1)
         self.assertCountSnapshots(1 + 1)
 
         self.assertRevisionsContain(revisions)
 
-        # TODO: how to check the snapshot id?
-        # self.assertSnapshotEqual(SNAPSHOT1)
-
         self.assertEqual(self.loader.load_status(), {"status": "eventful"})
         self.assertEqual(self.loader.visit_status(), "full")
 
@@ -262,27 +248,51 @@
         self.assertIsNotNone(visit["snapshot"])
         self.assertEqual(visit["status"], "full")
 
-        # Load with a new merge
-        self._git("merge", "branch1", "-m", "merge")
-        new_revision = self._git("rev-parse", "master").decode().strip()
+        snapshot_id = visit["snapshot"]
+        snapshot = self.storage.snapshot_get(snapshot_id)
+        branches = snapshot["branches"]
+        assert branches[b"HEAD"] == {
+            "target": b"refs/heads/master",
+            "target_type": "alias",
+        }
+        assert branches[b"refs/heads/master"] == {
+            "target": hash_to_bytes(new_revision),
+            "target_type": "revision",
+        }
 
-        assert new_revision not in revisions
-        revisions[new_revision] = "dab8a37df8db8666d4e277bef9a546f585b5bedd"
+        # Merge branch1 into HEAD.
+
+        current = self.repo[b"HEAD"]
+        branch1 = self.repo[b"refs/heads/branch1"]
+
+        merged_tree = dulwich.objects.Tree()
+        for item in self.repo[current.tree].items():
+            merged_tree.add(*item)
+        for item in self.repo[branch1.tree].items():
+            merged_tree.add(*item)
+
+        merged_dir_id = "dab8a37df8db8666d4e277bef9a546f585b5bedd"
+        assert merged_tree.id.decode() == merged_dir_id
+        self.repo.object_store.add_object(merged_tree)
+
+        merge_commit = self.repo.do_commit(
+            b"merge.\n", tree=merged_tree.id, merge_heads=[branch1.id]
+        )
+
+        assert merge_commit.decode() not in revisions
+        revisions[merge_commit.decode()] = merged_tree.id.decode()
 
         res = self.load()
         self.assertEqual(res["status"], "eventful")
 
         self.assertCountContents(4 + 1)
         self.assertCountDirectories(7 + 2)
-        self.assertCountReleases(0)  # FIXME: why not 2?
+        self.assertCountReleases(0)  # FIXME: should be 2 after T2059
         self.assertCountRevisions(7 + 2)
         self.assertCountSnapshots(1 + 1 + 1)
 
         self.assertRevisionsContain(revisions)
 
-        # TODO: how to check the snapshot id?
-        # self.assertSnapshotEqual(SNAPSHOT1)
-
         self.assertEqual(self.loader.load_status(), {"status": "eventful"})
         self.assertEqual(self.loader.visit_status(), "full")
 
@@ -290,6 +300,20 @@
         self.assertIsNotNone(visit["snapshot"])
         self.assertEqual(visit["status"], "full")
 
+        merge_snapshot_id = visit["snapshot"]
+        assert merge_snapshot_id != snapshot_id
+
+        merge_snapshot = self.storage.snapshot_get(merge_snapshot_id)
+        merge_branches = merge_snapshot["branches"]
+        assert merge_branches[b"HEAD"] == {
+            "target": b"refs/heads/master",
+            "target_type": "alias",
+        }
+        assert merge_branches[b"refs/heads/master"] == {
+            "target": hash_to_bytes(merge_commit.decode()),
+            "target_type": "revision",
+        }
+
 
 class GitLoaderFromArchiveTest(BaseGitLoaderFromArchiveTest, GitLoaderFromDiskTests):
     """Tests for GitLoaderFromArchive. Imports the common ones