Add a --files-from option about ack2 HOT 4 CLOSED

I wonder if there's a way we could also allow normal ack filters to be applied to this list? I found myself wanting the following today:

for file in $(ack --files-from=<(git ls-files --modified) --perl -f); do
  perl -c $file
done

(checks that all Perl files that have been changed compile)

from ack2.

This could also allow functionality like that requested in #35.

from ack2.

Expanding on how this would work with #35: we could have a way to alias option groupings, so ack --mtime=$mtime would translate to something like ack --files-from=<(find . -mtime $mtime), and ack --git-dirty would translates to something like ack --files-from=<$(git ls-files --modified).

from ack2.

This has been added.

from ack2.