commit: prepare repo_unuse_commit_buffer to handle any repo

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/commit.c b/commit.c
index 4034def..7d2f3a9 100644
--- a/commit.c
+++ b/commit.c
@@ -318,10 +318,12 @@ const void *repo_get_commit_buffer(struct repository *r,
 	return ret;
 }
 
-void unuse_commit_buffer(const struct commit *commit, const void *buffer)
+void repo_unuse_commit_buffer(struct repository *r,
+			      const struct commit *commit,
+			      const void *buffer)
 {
 	struct commit_buffer *v = buffer_slab_peek(
-		the_repository->parsed_objects->buffer_slab, commit);
+		r->parsed_objects->buffer_slab, commit);
 	if (!(v && v->buffer == buffer))
 		free((void *)buffer);
 }