Minor because normally only 1 FD is leaked per git-annex run. However,
the test suite leaks a few hundred FDs, and this broke it on the Debian
autobuilders, which seem to have a tigher than usual ulimit.
The leak was introduced by the lazy getDirectoryContents' that was
introduced in e6330988dd in order to scale to
millions of journal files -- if the lazy list was never fully consumed, the
directory handle did not get closed.
Instead, pull in openDirectory/readDirectory/closeDirectory code that I
already developed and submitted in a patch to the haskell directory library
earlier. Using this in journalDirty avoids the place that the lazy list
caused a problem. And using it in stageJournal eliminates the need for
getDirectoryContents'.
The getJournalFiles* functions are switched back to using the regular
strict getDirectoryContents. I'm not sure if those always consume the whole
list, so this avoids any leak. And the things that call those are things
like git annex unused, which also look at every file committed to the
git-annex branch, so would need more work to scale to insane numbers of
files anyway.