return git_default_config(var, value, cb);
 }
 
-static struct lock_file lock_file;
-
 int cmd_read_tree(int argc, const char **argv, const char *unused_prefix)
 {
        int i, stage = 0;
        struct tree_desc t[MAX_UNPACK_TREES];
        struct unpack_trees_options opts;
        int prefix_set = 0;
+       struct lock_file lock_file = LOCK_INIT;
        const struct option read_tree_options[] = {
                { OPTION_CALLBACK, 0, "index-output", NULL, N_("file"),
                  N_("write resulting index to <file>"),
                         N_("same as -m, but discard unmerged entries")),
                { OPTION_STRING, 0, "prefix", &opts.prefix, N_("<subdirectory>/"),
                  N_("read the tree into the index under <subdirectory>/"),
-                 PARSE_OPT_NONEG | PARSE_OPT_LITERAL_ARGHELP },
+                 PARSE_OPT_NONEG },
                OPT_BOOL('u', NULL, &opts.update,
                         N_("update working tree with merge result")),
                { OPTION_CALLBACK, 0, "exclude-per-directory", &opts,