refdb: add conditional symbolic updates

Add a parameter to the backend to allow checking for the old symbolic
target.

1 files changed, 18 insertions, 17 deletions

diff --git a/src/refdb_fs.c b/src/refdb_fs.c
index 554fe42c9..879e48514 100644
--- a/src/refdb_fs.c
+++ b/src/refdb_fs.c
@@ -936,12 +936,13 @@ static int refdb_fs_backend__write(
 	int force,
 	const git_signature *who,
 	const char *message,
-	const git_oid *old_id)
+	const git_oid *old_id,
+	const char *old_target)
 {
 	refdb_fs_backend *backend = (refdb_fs_backend *)_backend;
 	git_filebuf file = GIT_FILEBUF_INIT;
-	git_reference *old_ref;
-	int error = 0, cmp;
+	git_reference *old_ref = NULL;
+	int error = 0, cmp = 0;
 
 	assert(backend);
 
@@ -953,25 +954,25 @@ static int refdb_fs_backend__write(
 	if ((error = loose_lock(&file, backend, ref)) < 0)
 		return error;
 
-	if (old_id) {
+	if (old_id || old_target) {
 		if ((error = refdb_fs_backend__lookup(&old_ref, _backend, ref->name)) < 0)
 			goto on_error;
+	}
 
-		if (old_ref->type == GIT_REF_SYMBOLIC) {
-			git_reference_free(old_ref);
-			giterr_set(GITERR_REFERENCE, "cannot compare id to symbolic reference target");
-			error = -1;
-			goto on_error;
-		}
-
-		/* Finally we can compare the ids */
+	if (old_id && old_ref->type == GIT_REF_OID) {
 		cmp = git_oid_cmp(old_id, &old_ref->target.oid);
 		git_reference_free(old_ref);
-		if (cmp) {
-			giterr_set(GITERR_REFERENCE, "old reference value does not match");
-			error = GIT_EMODIFIED;
-			goto on_error;
-		}
+	}
+
+	if (old_target && old_ref->type == GIT_REF_SYMBOLIC) {
+		cmp = git__strcmp(old_target, old_ref->target.symbolic);
+		git_reference_free(old_ref);
+	}
+
+	if (cmp) {
+		giterr_set(GITERR_REFERENCE, "old reference value does not match");
+		error = GIT_EMODIFIED;
+		goto on_error;
 	}
 
 	if (should_write_reflog(backend->repo, ref->name) &&