Using --all, or running in a bare repo, as well as
`git annex unused` and `git annex info` all end up buffering the list of
all keys that have uncommitted journalled changes in memory.
This is due to Annex.Branch.files's call to getJournalledFilesStale which
reads all the files in the directory into a buffer.

Note that the list of keys in the branch *does* stream in, so this
is only really a problem when using annex.alwayscommit=false to build
up big git-annex branch commits via the journal.

An attempt at making it stream via unsafeInterleaveIO failed miserably
and that is not the right approach. This would be a good place to use
ResourceT, but it might need some changes to the Annex monad to allow
combining the two. --[[Joey]]

[[!tag confirmed]]
