Do no colorify test output if stdout is not a terminal

like when the output is redirected into a file in a cron job.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/test-lib.sh

@@ -60,6 +60,7 @@ esac
 # . ./test-lib.sh
 
 [ "x$TERM" != "xdumb" ] &&
+	[ -t 1 ] &&
 	tput bold >/dev/null 2>&1 &&
 	tput setaf 1 >/dev/null 2>&1 &&
 	tput sgr0 >/dev/null 2>&1 &&