Preparing for a release tomorrow. Yury fixed the Windows autobuilder over
the weekend. The OSX autobuilder was broken by my changes Friday, which
turned out to have a simple bug that took quite a long time to chase down.

Also added `git annex sync --content-of=path` to sync the contents of files
in a path, rather than in the whole work tree as `--content` does. I would
have rather made this be `--content=path` but optparse-applicative 
[does not support](https://github.com/pcapriotti/optparse-applicative/issues/243)
options that can be either boolean or have a string value. Really,
I'd rather `git annex sync path` do it, but that would be ambiguous
with the remote name parameter.

Today's work was sponsored by Jake Vosloo on Patreon.