I used to set GREP_OPTIONS to exclude *.orig and *.rej files. But with this
the test t4252-am-options.sh fails because it calls grep with a .rej file:

    grep "@@ -1,3 +1,3 @@" file-2.rej
Signed-off-by: NBert Wesarg <bert.wesarg@googlemail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>