From efe3045aaf9fdaa726776d911c6c2fa109c90af9 Mon Sep 17 00:00:00 2001
From: Runxi Yu
Date: Sat, 28 Mar 2026 17:52:42 +0000
Subject: repository: Add commit-graph

---
 repository/close.go        |  7 +++++++
 repository/commit_graph.go | 37 +++++++++++++++++++++++++++++++++++++
 repository/open.go         |  7 +++++++
 repository/repository.go   |  8 +++++---
 4 files changed, 56 insertions(+), 3 deletions(-)
 create mode 100644 repository/commit_graph.go

diff --git a/repository/close.go b/repository/close.go
index fa6f8f85..5d728c5b 100644
--- a/repository/close.go
+++ b/repository/close.go
@@ -22,6 +22,13 @@ func (repo *Repository) Close() error {
 		}
 	}
 
+	if repo.commitGraph != nil {
+		err := repo.commitGraph.Close()
+		if err != nil {
+			errs = append(errs, err)
+		}
+	}
+
 	if repo.objectsPacked != nil {
 		err := repo.objectsPacked.Close()
 		if err != nil {
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
+}
diff --git a/repository/open.go b/repository/open.go
index 0e47ba83..f4dd78f8 100644
--- a/repository/open.go
+++ b/repository/open.go
@@ -44,6 +44,13 @@ func Open(root *os.Root) (repo *Repository, err error) {
 	repo.objectsLoose = objectsLoose
 	repo.objectsPacked = objectsPacked
 
+	commitGraph, err := openCommitGraph(objectsRoot, algo)
+	if err != nil {
+		return nil, err
+	}
+
+	repo.commitGraph = commitGraph
+
 	refRoot, err := root.OpenRoot(".")
 	if err != nil {
 		return nil, fmt.Errorf("repository: open root for refs: %w", err)
diff --git a/repository/repository.go b/repository/repository.go
index 8c7c091f..b60e0023 100644
--- a/repository/repository.go
+++ b/repository/repository.go
@@ -5,6 +5,7 @@ import (
 	"os"
 
 	"codeberg.org/lindenii/furgit/config"
+	commitgraphread "codeberg.org/lindenii/furgit/format/commitgraph/read"
 	objectid "codeberg.org/lindenii/furgit/object/id"
 	objectstore "codeberg.org/lindenii/furgit/object/store"
 	objectloose "codeberg.org/lindenii/furgit/object/store/loose"
@@ -18,9 +19,9 @@ import (
 // Open expects a root for the Git directory itself:
 // a bare repository root or a non-bare ".git" directory.
 //
-// Accessors such as [Repository.Objects], [Repository.Refs],
-// [Repository.Fetcher], and [Repository.LooseStoreForWriting] return
-// repository-backed views.
+// Accessors such as [Repository.Objects], [Repository.CommitGraph],
+// [Repository.Refs], [Repository.Fetcher], and
+// [Repository.LooseStoreForWriting] return repository-backed views.
 //
 // Labels: MT-Safe, Close-Caller.
 type Repository struct {
@@ -32,6 +33,7 @@ type Repository struct {
 	objectsPackRoot *os.Root
 	objectsLoose    *objectloose.Store
 	objectsPacked   *objectpacked.Store
+	commitGraph     *commitgraphread.Reader
 	refRoot         *os.Root
 	refs            refstore.ReadWriteStore
 }
-- 
cgit v1.3.1-10-gc9f91