1 files changed, 37 insertions, 0 deletions
diff --git a/repository/commit_graph.go b/repository/commit_graph.go
new file mode 100644
index 00000000..b45d9da0
--- /dev/null
+++ b/repository/commit_graph.go
@@ -0,0 +1,37 @@
+package repository
+
+import (
+	"errors"
+	"os"
+
+	commitgraphread "codeberg.org/lindenii/furgit/format/commitgraph/read"
+	objectid "codeberg.org/lindenii/furgit/object/id"
+)
+
+func openCommitGraph(root *os.Root, algo objectid.Algorithm) (*commitgraphread.Reader, error) {
+	reader, err := commitgraphread.Open(root, algo, commitgraphread.OpenChain)
+	if err == nil {
+		return reader, nil
+	}
+
+	var malformed *commitgraphread.MalformedError
+	if errors.As(err, &malformed) &&
+		malformed.Path == "info/commit-graphs/commit-graph-chain" &&
+		malformed.Reason == "missing commit-graph-chain" {
+		reader, err = commitgraphread.Open(root, algo, commitgraphread.OpenSingle)
+		if errors.Is(err, os.ErrNotExist) {
+			return nil, nil
+		}
+
+		return reader, err
+	}
+
+	return nil, err
+}
+
+// CommitGraph returns the configured commit-graph reader, if available.
+//
+// Labels: Life-Parent, Close-No.
+func (repo *Repository) CommitGraph() *commitgraphread.Reader {
+	return repo.commitGraph
+}