### Please describe the problem.

`uuid.log` can end up in a state where `git annex describe` (and probably other things) stops working.

### What steps will reproduce the problem?

Run `git annex describe` against a remote that is not a an initialized git-annex repo.

### What version of git-annex are you using? On what operating system?

debian-packaged git-annex 4.20131106 on Linux Mint 13/Maya (Ubuntu Precise/12.04)

### Please provide any additional information below.

I will follow comments, but can also be found at [[https://microca.st/clacke]].

Full transcript to reproduce:

[[!format sh """
$ git init a
Initialized empty Git repository in /tmp/annex/a/.git/
$ git init b
Initialized empty Git repository in /tmp/annex/b/.git/
$ cd a/
$ git annex init
init  ok
(Recording state in git...)
$ git remote add -f b ../b
Updating b
$ git annex describe b b # this should not be ok
describe b ok
(Recording state in git...)
$ git annex describe b b
describe b git-annex: Prelude.last: empty list
$ git cat-file blob git-annex:uuid.log
 b timestamp=1383987654.900868s
...

# End of transcript.
"""]]

> Fixed the bug and made git breakage not crash git-annex. [[done]]
> --[[Joey]] 

> > Update: Also made it automatically clean up the cruft this put in the
> > log. --[[Joey]] 
