commit: make it work with status.short

With "status.short" set, it is now impossible to commit with
status.short set, because it acts like "git commit --short", and it
is impossible to differentiate between a status_format set by the
command-line option parser versus that set by the config parser.

To alleviate this problem, clear status_format as soon as the config
parser has finished its work.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/commit.c

@@ -1441,6 +1441,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 	wt_status_prepare(&s);
 	gitmodules_config();
 	git_config(git_commit_config, &s);
+	status_format = STATUS_FORMAT_NONE; /* Ignore status.short */
 	determine_whence(&s);
 	s.colopts = 0;