### Please describe the problem.

i can't find a key in the JSON output of `git annex info` for the "transfer in progress" field. is it missing on purpose? or am I missing some field?

### What steps will reproduce the problem?

<pre>
git annex info
git annex info --json
</pre>


### What version of git-annex are you using? On what operating system?
5.20150406-g2a9fbec debian jessie

### 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
anarcat@desktop008:mp3$ git annex info  --fast --json | grep -i transfer
anarcat@desktop008:mp3$ git annex info  --fast | grep -i transfer
transfers in progress:

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

[[anarcat]]

> JSON output has to be implemented on a case by case basis for stat
> displays; I've now added it to this and more. [[done]]
> --[[Joey]]
