### Please describe the problem.
Doing a git annex command while passing a bad --git-dir can result in the .git directory being deleted. I've never experienced it with plain git, so I assume that it comes for annex.

### What steps will reproduce the problem?

[[!format sh """
$ mkdir annex_destroyed_my_git_directory
$ cd annex_destroyed_my_git_directory
$ git init
$ git annex init
$ ls -a
. .. .git
$ git --git-dir=$PWD annex find
fatal: Not a git repository: '/home/doudou/tmp/annex_destroyed_my_git_directory'
$ ls -a
. .. config
"""]]

### What version of git-annex are you using? On what operating system?
dpkg -l git-annex reports 5.20141024

I am running Debian sid.

### 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.
"""]]

> [[fixed|done]] --[[Joey]]
