git.el: Improve error handling for commits.

diff --git a/builtin-diff-index.c b/builtin-diff-index.c
index 17d851b29ee5de33e01745eabcd5cd735c30b352..04837494feba401c7f689eab5574768d3fd126de 100644 (file)
--- a/builtin-diff-index.c
+++ b/builtin-diff-index.c
@@ -39,6 +39,8 @@ int cmd_diff_index(int argc, const char **argv, const char *prefix)
        if (rev.pending.nr != 1 ||
            rev.max_count != -1 || rev.min_age != -1 || rev.max_age != -1)
                usage(diff_cache_usage);
+       if (!cached)
+               setup_work_tree();
        if (read_cache() < 0) {
                perror("read_cache");
                return -1;