[PATCH 4/4] diff --stat: do not run diff on indentical files

From: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Date: May 1, 2012, 17:10 UTC
Message-ID: <1335892215-21331-5-git-send-email-zbyszek@in.waw.pl>
In-Reply-To: <1335892215-21331-1-git-send-email-zbyszek@in.waw.pl>

If sha1's are equal, then there's no point in performing the diff.

In a very unscientific test:

git init &&
  dd if=/dev/urandom bs=1M count=30 | hexdump >file1 &&
  git add file1 && git commit -m 'add file' &&
  git mv file1 file1-moved && chmod +x file1-moved &&
  command time git diff --stat

(before) git diff --stat 2.00s user 0.31s system 99% cpu 2.323 total (after) git diff --stat 0.80s user 0.10s system 98% cpu 0.913 total

Signed-off-by: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
---
 diff.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/diff.c b/diff.c
index 6eb2946..7cb9893 100644
--- a/diff.c
+++ b/diff.c
@@ -2398,7 +2398,7 @@ static void builtin_diffstat(const char *name_a, const char *name_b,
 		data->added = count_lines(two->data, two->size);
 	}
 
-	else {
+	else if (!data->is_unchanged) {
 		/* Crazy xdl interfaces.. */
 		xpparam_t xpp;
 		xdemitconf_t xecfg;

-- 
1.7.10.539.g288dd