bug#22144: --exclude no longer works against arguments with a directory name

[Paul Eggert]

The change in grep 2.22 is due to an earlier bug report:
http://bugs.gnu.org/21027

and was implemented by this patch:

http://git.savannah.gnu.org/cgit/grep.git/commit/?id=c5c70eae261133d71a9436557d998a48aaf0a5fe

Although I can see arguments either way, the grep 2.22 behavior is 
consistent with grep 2.6 and earlier, so in some sense it's 
more-conservative.