use xstrncmpz()

Add and apply a semantic patch for calling xstrncmpz() to compare a
NUL-terminated string with a buffer of a known length instead of using
strncmp() and checking the terminating NUL explicitly.  This simplifies
callers by reducing code duplication.

I had to adjust remote.c manually because Coccinelle inexplicably
changed the indent of the else branches.

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

merge-ll.c

@@ -286,7 +286,7 @@ static int read_merge_config(const char *var, const char *value,
 	 * after seeing merge.<name>.var1.
 	 */
 	for (fn = ll_user_merge; fn; fn = fn->next)
-		if (!strncmp(fn->name, name, namelen) && !fn->name[namelen])
+		if (!xstrncmpz(fn->name, name, namelen))
 			break;
 	if (!fn) {
 		CALLOC_ARRAY(fn, 1);