Re: Use a *real* built-in diff generator

On Sat, 25 Mar 2006, Linus Torvalds wrote:

I'll be taking a look at trying to fix it. 

Actually, it ended up being easier than I expected it to be.

This (on top of the previous patch) should fix it.

And yes, with this, I can pass the output of

	git diff v2.6.16..

to "git-apply" and it not only passes the "--stat" thing (which verifies 
that git-apply is happy with the diff) but it also results in exactly the 
same tree when applied on top of v2.6.16 (and the patch has two cases 
where the "no newline" test triggers).

The speed-up is quite noticeable, especially when doing things like

	git diff v2.6.16.. | git-apply --stat

which just _used_ to be painfully slow (25 seconds for me) and is now 
under five seconds. That's the difference between "twiddling your thumbs" 
and "ok, that wasn't too bad".

Now, to be honest, the real reason I wanted a built-in diff wasn't the 
speed advantage, but the fact that it's so much more flexible. The lack of 
fork/exec just allows us to do things that weren't practical before.

		Linus

----

diff --git a/xdiff/xutils.c b/xdiff/xutils.c
index 01e6765..b68afa2 100644
--- a/xdiff/xutils.c
+++ b/xdiff/xutils.c

@@ -31,14 +31,22 @@
 
 int xdl_emit_diffrec(char const *rec, long size, char const *pre, long psize,
 		     xdemitcb_t *ecb) {
-	mmbuffer_t mb[2];
+	mmbuffer_t mb[3];
+	int i;
 
 	mb[0].ptr = (char *) pre;
 	mb[0].size = psize;
 	mb[1].ptr = (char *) rec;
 	mb[1].size = size;
+	i = 2;
 
-	if (ecb->outf(ecb->priv, mb, 2) < 0) {
+	if (!size || rec[size-1] != '\n') {
+		mb[2].ptr = "\n\\ No newline at end of file\n";
+		mb[2].size = strlen(mb[2].ptr);
+		i = 3;
+	}
+
+	if (ecb->outf(ecb->priv, mb, i) < 0) {
 
 		return -1;
 	}