[PATCH v2 6/8] commit-graph: not compatible with grafts

[Derrick Stolee <dstolee@microsoft.com>]

Augment commit_graph_compatible(r) to return false when the given
repository r has commit grafts or is a shallow clone. Test that in these
situations we ignore existing commit-graph files and we do not write new
commit-graph files.

Helped-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 commit-graph.c          |  6 ++++++
 commit.c                |  2 +-
 commit.h                |  1 +
 t/t5318-commit-graph.sh | 38 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/commit-graph.c b/commit-graph.c
index 2c01fa433f..c4eaedf4e5 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -68,6 +68,12 @@ static int commit_graph_compatible(struct repository *r)
 			return 0;
 	}
 
+	prepare_commit_graft(r);
+	if (r->parsed_objects && r->parsed_objects->grafts_nr)
+		return 0;
+	if (is_repository_shallow(r))
+		return 0;
+
 	return 1;
 }
 
diff --git a/commit.c b/commit.c
index 30d1af2b20..ef9a2cbb23 100644
--- a/commit.c
+++ b/commit.c
@@ -209,7 +209,7 @@ static int read_graft_file(struct repository *r, const char *graft_file)
 	return 0;
 }
 
-static void prepare_commit_graft(struct repository *r)
+void prepare_commit_graft(struct repository *r)
 {
 	char *graft_file;
 
diff --git a/commit.h b/commit.h
index da0db36eba..5459e279fe 100644
--- a/commit.h
+++ b/commit.h
@@ -202,6 +202,7 @@ typedef int (*each_commit_graft_fn)(const struct commit_graft *, void *);
 
 struct commit_graft *read_graft_line(struct strbuf *line);
 int register_commit_graft(struct repository *r, struct commit_graft *, int);
+void prepare_commit_graft(struct repository *r);
 struct commit_graft *lookup_commit_graft(struct repository *r, const struct object_id *oid);
 
 extern struct commit_list *get_merge_bases(struct commit *rev1, struct commit *rev2);
diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh
index e0c3c60f66..6aee861f78 100755
--- a/t/t5318-commit-graph.sh
+++ b/t/t5318-commit-graph.sh
@@ -281,6 +281,44 @@ test_expect_success 'replace-objects invalidates commit-graph' '
 	)
 '
 
+test_expect_success 'commit grafts invalidate commit-graph' '
+	cd "$TRASH_DIRECTORY" &&
+	test_when_finished rm -rf graft &&
+	git clone full graft &&
+	(
+		cd graft &&
+		git commit-graph write --reachable &&
+		test_path_is_file .git/objects/info/commit-graph &&
+		H1=$(git rev-parse --verify HEAD~1) &&
+		H3=$(git rev-parse --verify HEAD~3) &&
+		echo "$H1 $H3" >.git/info/grafts &&
+		git -c core.commitGraph=false log >expect &&
+		git -c core.commitGraph=true log >actual &&
+		test_cmp expect actual &&
+		git commit-graph write --reachable &&
+		git -c core.commitGraph=false --no-replace-objects log >expect &&
+		git -c core.commitGraph=true --no-replace-objects log >actual &&
+		test_cmp expect actual &&
+		rm -rf .git/objects/info/commit-graph &&
+		git commit-graph write --reachable &&
+		test_path_is_missing .git/objects/info/commit-graph
+	)
+'
+
+test_expect_success 'replace-objects invalidates commit-graph' '
+	cd "$TRASH_DIRECTORY" &&
+	test_when_finished rm -rf shallow &&
+	git clone --depth 2 "file://$TRASH_DIRECTORY/full" shallow &&
+	(
+		cd shallow &&
+		git commit-graph write --reachable &&
+		test_path_is_missing .git/objects/info/commit-graph &&
+		git fetch origin --unshallow &&
+		git commit-graph write --reachable &&
+		test_path_is_file .git/objects/info/commit-graph
+	)
+'
+
 # the verify tests below expect the commit-graph to contain
 # exactly the commits reachable from the commits/8 branch.
 # If the file changes the set of commits in the list, then the
-- 
2.18.0.118.gd4f65b8d14