Useful for dropping old objects from cache repositories.
But also, quite a genrally useful thing to have..
Rather than imitiating find's -atime and other options, all of which are
pretty horrible to use, I made this match files accessed within a time
period, using the same duration format used by git-annex schedule and
--limit-time
In passing, changed the --limit-time option parser to parse the
duration, instead of having it later throw an error.
This commit was supported by the NSF-funded DataLad project.
Added --securehash option to match files using a secure hash function, and
corresponding securehash preferred content expression.
This commit was sponsored by Ethan Aubin.
