### Please describe the problem.
When the preferred content for a repo is greater than the free space on the drive for me, the space becomes exhausted due to upload that occurs during syncing -- the git history ends up exhausting the space.  The result for me has been corrupted repos with broken refs and heads.

I think it would be better if the git syncing process respected the same space limitations that the content syncing does, and did not push if space was exhausted on the destination, nor pull if space exhausted locally.

### What steps will reproduce the problem?
Make enough git commits that it exhausts the free space on some repo.

### What version of git-annex are you using? On what operating system?
I've been using a few different versions; right now I am using 6.2016-0511 and 6.2016-0517-g766728c
but I have not tested this issue with these most recent versions.  I am still trying to get my smaller repos back together.

### Please provide any additional information below.

[[!format sh """
# If you can, paste a complete transcript of the problem occurring here.
# If the problem is with the git-annex assistant, paste in .git/annex/daemon.log


# End of transcript or log.
"""]]

### Have you had any luck using git-annex before? (Sometimes we get tired of reading bug reports all day and a lil' positive end note does wonders)

Yes !!! I'm moving all my files into my annex.  It is very robust; whenever something is wrong there is always some other copy somewhere that can be used.

