Some of the things git-annex transferkeys does are suboptimal, especially
when -J has many of them running.

In particular, it writes location logs when downloading (but not
uploading), and so it flushes the journal etc.

> [[done]] --[[Joey]] 

It may also do some queries of data from git that could be avoided with
some refactoring of what code runs in it, which could avoid it needing to
start up git helper processes like catkey. --[[Joey]]

> Still starts some git catkey processes, but I guess it's for good reason.
> --[[Joey]]
