sha1_file: release strbuf on error return in index_path()

strbuf_readlink() already frees the buffer for us on error.  Clean up
if write_sha1_file() fails as well instead of returning early.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: rscharfe

sha1_file.c

@@ -1820,6 +1820,7 @@ int index_path(struct object_id *oid, const char *path, struct stat *st, unsigne
 {
 	int fd;
 	struct strbuf sb = STRBUF_INIT;
+	int rc = 0;
 
 	switch (st->st_mode & S_IFMT) {
 	case S_IFREG:
@@ -1836,16 +1837,15 @@ int index_path(struct object_id *oid, const char *path, struct stat *st, unsigne
 		if (!(flags & HASH_WRITE_OBJECT))
 			hash_sha1_file(sb.buf, sb.len, blob_type, oid->hash);
 		else if (write_sha1_file(sb.buf, sb.len, blob_type, oid->hash))
-			return error("%s: failed to insert into database",
-				     path);
+			rc = error("%s: failed to insert into database", path);
 		strbuf_release(&sb);
 		break;
 	case S_IFDIR:
 		return resolve_gitlink_ref(path, "HEAD", oid->hash);
 	default:
 		return error("%s: unsupported file type", path);
 	}
-	return 0;
+	return rc;
 }
 
 int read_pack_header(int fd, struct pack_header *header)