Don't try to pack symbolic refs

If there were symbolic refs among the loose refs then the code
to create packed-refs would fail trying to parse the OID out of
them (where Git just skips trying to pack them).  This fixes it.

src/refdb_fs.c

@@ -316,6 +316,12 @@ static int loose_lookup_to_packfile(
 	if (reference_read(&ref_file, NULL, backend->path, name, NULL) < 0)
 		return -1;
 
+	/* skip symbolic refs */
+	if (!git__prefixcmp(git_buf_cstr(&ref_file), GIT_SYMREF)) {
+		git_buf_free(&ref_file);
+		return 0;
+	}
+
 	git_buf_rtrim(&ref_file);
 
 	name_len = strlen(name);
@@ -355,6 +361,9 @@ static int _dirent_loose_load(void *data, git_buf *full_path)
 	if (loose_lookup_to_packfile(&ref, backend, file_path) < 0)
 		return -1;
 
+	if (!ref)
+		return 0;
+
 	git_strmap_insert2(
 		backend->refcache.packfile, ref->name, ref, old_ref, err);
 	if (err < 0) {
@@ -460,7 +469,7 @@ static int loose_lookup(
 	if (error < 0)
 		goto done;
 
-	if (git__prefixcmp((const char *)(ref_file.ptr), GIT_SYMREF) == 0) {
+	if (git__prefixcmp(git_buf_cstr(&ref_file), GIT_SYMREF) == 0) {
 		git_buf_rtrim(&ref_file);
 
 		if ((target = loose_parse_symbolic(&ref_file)) == NULL) {

tests-clar/refs/pack.c

@@ -32,7 +32,7 @@ static void packall(void)
 
 void test_refs_pack__empty(void)
 {
-   // create a packfile for an empty folder
+	/* create a packfile for an empty folder */
 	git_buf temp_path = GIT_BUF_INIT;
 
 	cl_git_pass(git_buf_join_n(&temp_path, '/', 3, git_repository_path(g_repo), GIT_REFS_HEADS_DIR, "empty_dir"));
@@ -44,7 +44,7 @@ void test_refs_pack__empty(void)
 
 void test_refs_pack__loose(void)
 {
-   // create a packfile from all the loose rn a repo
+	/* create a packfile from all the loose rn a repo */
 	git_reference *reference;
 	git_buf temp_path = GIT_BUF_INIT;
 
@@ -77,3 +77,29 @@ void test_refs_pack__loose(void)
 	git_reference_free(reference);
 	git_buf_free(&temp_path);
 }
+
+void test_refs_pack__symbolic(void)
+{
+	/* create a packfile from loose refs skipping symbolic refs */
+	int i;
+	git_oid head;
+	git_reference *ref;
+	char name[128];
+
+	cl_git_pass(git_reference_name_to_id(&head, g_repo, "HEAD"));
+
+	/* make a bunch of references */
+
+	for (i = 0; i < 100; ++i) {
+		snprintf(name, sizeof(name), "refs/heads/symbolic-%03d", i);
+		cl_git_pass(git_reference_symbolic_create(
+			&ref, g_repo, name, "refs/heads/master", 0));
+		git_reference_free(ref);
+
+		snprintf(name, sizeof(name), "refs/heads/direct-%03d", i);
+		cl_git_pass(git_reference_create(&ref, g_repo, name, &head, 0));
+		git_reference_free(ref);
+	}
+
+	packall();
+}