[PATCH] Built-in diff driver shows Index: line.

As suggested by Linus as a workaround to unconfuse diffstat,
this patch adds Index: line before the diff output the built-in
driver produces.

Signed-off-by: Junio C Hamano <redacted>
---

diff.c |    2 ++
1 files changed, 2 insertions(+)

# - 04/28 11:20 No need to say diff-tree -p -r in git-export
# + 04/28 11:25 Show Index: line from built-in diff driver.
Index: diff.c

--- k/diff.c  (mode:100644)
+++ l/diff.c  (mode:100644)

@@ -125,6 +125,8 @@ static void builtin_diff(const char *nam
 	next_at += snprintf(cmd+next_at, cmd_size-next_at,
 			    diff_arg, input_name_sq[0], input_name_sq[1]);
 
+	printf("Index: %s\n", name);
+	fflush(NULL);
 	execlp("/bin/sh","sh", "-c", cmd, NULL);
 }