Make sample pre-commit hook output Emacs friendly.

Use the common error message format, "filename:lineno: body";
this way, problematic lines can be jumped to from the Emacs
compilation buffer by C-x `.

Signed-off-by: Junio C Hamano <junkio@cox.net>

templates/hooks--pre-commit

@@ -28,7 +28,8 @@ perl -e '
 	    print "* In $filename\n";
 	    $reported_filename = $filename;
 	}
-	print "* $why (line $lineno)\n$line\n";
+	print "* $why (line $lineno)\n";
+	print "$filename:$lineno:$line\n";
     }
     open $fh, "-|", qw(git-diff-cache -p -M --cached HEAD);
     while (<$fh>) {