Make sanity checker run git annex unused daily, and queue up transfers
of unused files to any remotes that will have them. The transfer retrying
code works for us here, so eg when a backup disk remote is plugged in,
any transfers to it are done. Once the unused files reach a remote,
they'll be removed locally as unwanted.
If the setup does not cause unused files to go to a remote, they'll pile
up, and the sanity checker detects this using some heuristics that are
pretty good -- 1000 unused files, or 10% of disk used by unused files,
or more disk wasted by unused files than is left free. Once it detects
this, it pops up an alert in the webapp, with a button to take action.
TODO: Webapp UI to configure this, and also the ability to launch an
immediate cleanup of all unused files.
This commit was sponsored by Simon Michael.
This will be used in expiring old unused objects. The timestamp is when it
was first noticed it was unused.
Backwards compatability: It supports reading old format unused log files.
The old version of git-annex will ignore lines in log files written by the
new version, so the worst interop problem would be git annex dropunused not
knowing some numbers that git-annex unused reported.
This commit includes a paydown on technical debt incurred two years ago,
when I didn't know that it was bad to make custom Read and Show instances
for types. As the routes need Read and Show for Transfer, which includes a
Key, and deriving my own Read instance of key was not practical,
I had to finally clean that up.
So the compact Key read and show functions are now file2key and key2file,
and Read and Show are now derived instances.
Changed all code that used the old instances, compiler checked.
(There were a few places, particularly in Command.Unused, and the test
suite where the Show instance continue to be used for legitimate
comparisons; ie show key_x == show key_y (though really in a bloom filter))
