t0027: make commit_chk_wrnNNO() reliable

When the content of a commited file is unchanged and the attributes
are changed, Git may not detect that the next commit must treat the
file as changed.  This happens when lstat() doesn't detect a change,
since neither inode, mtime nor size are changed.

Add a single "Z" character to change the file size and content.
When the files are compared later in checkout_files(), the "Z" is
removed before the comparison.

Signed-off-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t0027-auto-crlf.sh

@@ -12,7 +12,7 @@ fi
 
 compare_files () {
 	tr '\015\000' QN <"$1" >"$1".expect &&
-	tr '\015\000' QN <"$2" >"$2".actual &&
+	tr '\015\000' QN <"$2" | tr -d 'Z' >"$2".actual &&
 	test_cmp "$1".expect "$2".actual &&
 	rm "$1".expect "$2".actual
 }
@@ -114,6 +114,7 @@ commit_chk_wrnNNO () {
 	do
 		fname=${pfx}_$f.txt &&
 		cp $f $fname &&
+		printf Z >>"$fname" &&
 		git -c core.autocrlf=$crlf add $fname 2>/dev/null &&
 		git -c core.autocrlf=$crlf commit -m "commit_$fname" $fname >"${pfx}_$f.err" 2>&1
 	done