Merge pull request #556 from koordinates/issue-555

Fix for #555 - issues with merge + shallow clones

CHANGELOG.md

@@ -16,6 +16,7 @@ Support for spatial filters - the spatial filter can be updated during an `init`
 * Bugfix: better error message when `kart import` fails due to multiple XML metadata files for a single dataset, which Kart does not support [#547](https://github.com/koordinates/kart/issues/547)
 * When there are two pieces of XML metadata for a single dataset, but one is simply a `GDALMultiDomainMetadata` wrapping the other, the wrapped version is ignored. [#547](https://github.com/koordinates/kart/issues/547)
 * Bugfix: fixed a bug preventing `checkout -b NEW_BRANCH HEAD^` and similar commands from working
+* Bugfix: fixed a bug where `kart merge` would fail in a shallow clone, in certain circumstances. [#555](https://github.com/koordinates/kart/issues/555)
 
 ## 0.10.8
 

kart/repo.py

@@ -780,6 +780,18 @@ def revparse_ext(self, revision):
             revision = "HEAD"
         return super().revparse_ext(revision)
 
+    def merge_base(self, oid1, oid2):
+        # FIXME: Overridden to work around https://github.com/koordinates/kart/issues/555
+        # Caused by https://github.com/libgit2/libgit2/issues/6123
+        try:
+            args = ["git", "-C", self.path, "merge-base", str(oid1), str(oid2)]
+            output = subprocess.check_output(
+                args, encoding="utf8", env=tool_environment()
+            )
+            return pygit2.Oid(hex=output.strip())
+        except subprocess.CalledProcessError:
+            return None
+
     KART_COMMON_README = [
         "",
         "kart status",

tests/test_merge.py

@@ -208,6 +208,31 @@ def test_merge_true(
             assert rowcount == num_inserts
 
 
+def test_merge_shallow_clone(data_archive, tmp_path, cli_runner):
+    with data_archive("points") as repo1_path:
+        repo1_url = f"file://{repo1_path.resolve()}"
+        repo2_path = tmp_path / "repo2"
+
+        # Clone only 1 commit from repo with more than one commit:
+        r = cli_runner.invoke(["clone", repo1_url, repo2_path, "--depth=1"])
+        assert r.exit_code == 0, r.stderr
+
+        # Make a simple commit with that one commit as a parent.
+        r = cli_runner.invoke(["-C", repo2_path, "commit-files", "-m", "A1", "a=1"])
+        assert r.exit_code == 0, r.stderr
+
+        r = cli_runner.invoke(["-C", repo2_path, "checkout", "HEAD^"])
+        assert r.exit_code == 0, r.stderr
+
+        # Make another simple commit that clearly doesn't conflict, with the same parent.
+        r = cli_runner.invoke(["-C", repo2_path, "commit-files", "-m", "B2", "b=2"])
+        assert r.exit_code == 0, r.stderr
+
+        # Merge them together.
+        r = cli_runner.invoke(["-C", repo2_path, "merge", "main", "-m", "merged"])
+        assert r.exit_code == 0, r.stderr
+
+
 @pytest.mark.parametrize(
     "data",
     [