init.sh: sync from gnulib

[Jim Meyering]

FYI,

>From a4fa14849a7e310d135732142df2439f8f820483 Mon Sep 17 00:00:00 2001
From: Bruno Haible <address@hidden>
Date: Mon, 19 Sep 2011 19:24:35 +0200
Subject: [PATCH] tests: init.sh: support any non-GNU diff

* tests/init.sh (compare): If "diff -c" is supported but "diff -u" is
not, use "diff -c".  Useful on AIX 6.1, HP-UX 11.31, OSF/1 5.1,
Solaris 8.
---
 tests/init.sh |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/tests/init.sh b/tests/init.sh
index 12b3ca3..373d9d4 100644
--- a/tests/init.sh
+++ b/tests/init.sh
@@ -223,6 +223,8 @@ cleanup_ () { :; }

 if ( diff -u "$0" "$0" < /dev/null ) > /dev/null 2>&1; then
   compare () { diff -u "$@"; }
+elif ( diff -c "$0" "$0" < /dev/null ) > /dev/null 2>&1; then
+  compare () { diff -c "$@"; }
 elif ( cmp --version < /dev/null 2>&1 | grep GNU ) > /dev/null 2>&1; then
   compare () { cmp -s "$@"; }
 else
--
1.7.7.rc0.362.g5a14