(AT_INIT): Don't accept Solaris 9's diff -u, since it outputs chatter

if the input files are the same.  Problem reported by Ralf Menzel.

diff --git a/lib/autotest/general.m4 b/lib/autotest/general.m4
index ec741ce0a0a4a2d61e4addc041bd27a578dda9d6..04306b9a82d047cb4cec0ef303c081691c3d0ff1 100644 (file)
--- a/lib/autotest/general.m4
+++ b/lib/autotest/general.m4
@@ -610,7 +610,8 @@ else
 fi
 
 # Use `diff -u' when possible.
-if diff -u "$at_devnull" "$at_devnull" >/dev/null 2>&1; then
+if at_diff=`diff -u "$at_devnull" "$at_devnull" 2>&1` && test -z "$at_diff"
+then
   at_diff='diff -u'
 else
   at_diff=diff