### Please describe the problem.

[[git-annex-shell]] seems to be designed to be put as some users' shells so that git-annex can be safely used from `sshd`.

### What steps will reproduce the problem?

<pre>
root@cs:/srv/gitannex-test# grep gitannex /etc/passwd
gitannex:x:999:999:Git annex sandbox:/var/lib/gitannex:/usr/local/bin/git-annex-shell
</pre>

`/usr/local/bin/git-annex-shell` is a symlink to the standalone git-annex installed in `/opt`.

<pre>
anarcat@desktop008:isuma-annex-test$ git remote -v
origin  gitannex@example.com:/srv/gitannex-test (fetch)
anarcat@desktop008:isuma-annex-test$ git annex sync
muxserver_listen: link mux listener .git/annex/ssh/gitannex@example.com.bFOddoa2pVKZGHQ2 => .git/annex/ssh/gitannex@example.com: Operation not permitted

  Remote origin does not have git-annex installed; setting annex-ignore

  This could be a problem with the git-annex installation on the remote. Please make sure that git-annex-shell is available in PATH when you ssh into the remote. Once you have fixed the git-annex installation, run: git config remote.origin.annex-ignore false
commit  ok
pull origin
git-annex: unknown command gitannex@cs.isuma.tv

Usage: git-annex command [option ...]

Commonly used commands:

add             [PATH ...]         add files to annex
[...]

Testing commands:

fuzztest                           generates fuzz test files
test                               run built-in test suite
testremote      REMOTE             test transfers to/from a remote

fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.
failed
push origin
git-annex: unknown command gitannex@cs.isuma.tv

Usage: git-annex command [option ...]

Commonly used commands:

add             [PATH ...]         add files to annex
[...]
Testing commands:

fuzztest                           generates fuzz test files
test                               run built-in test suite
testremote      REMOTE             test transfers to/from a remote

fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

  Pushing to origin failed.

  (non-fast-forward problems can be solved by setting receive.denyNonFastforwards to false in the remote's git config)
failed
git-annex: sync: 2 failed
</pre>

Note that moving the repository out of NFS doesn't fix the problem, i still get `git-annex: unknown command gitannex@cs.isuma.tv`.

How am i supposed to use `git-annex-shell`? -- [[anarcat]]

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

client side: 5.20141125

server side: 5.20150406-g2a9fbec

### 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.
"""]]

Update: well that's confusing. it turns out the `unknown command` bit still happens when i use `/bin/sh` as a shell for the gitannex user. i really don't understand what's going on here... :/

After running with `--debug`, i noticed this was happening on the client with any git-annex remote, including one running the same version (`5.20141125`), and it happens after `git-annex` calls `git push` or `git fetch`:

<pre>
anarcat@desktop008:isuma-annex-test$ git annex --debug sync test3
[2015-04-06 16:52:36 EDT] read: git ["--git-dir=/srv/scratch/anarcat/isuma-annex-test/.git","--work-tree=/srv/scratch/anarcat/isuma-annex-test","show-ref","git-annex"]
[2015-04-06 16:52:36 EDT] read: git ["--git-dir=/srv/scratch/anarcat/isuma-annex-test/.git","--work-tree=/srv/scratch/anarcat/isuma-annex-test","show-ref","--hash","refs/heads/git-annex"]
[2015-04-06 16:52:36 EDT] read: git ["--git-dir=/srv/scratch/anarcat/isuma-annex-test/.git","--work-tree=/srv/scratch/anarcat/isuma-annex-test","log","refs/heads/git-annex..41069ddc0e22abc7ef0dca2aa31b20af9cee6116","-n1","--pretty=%H"]
[2015-04-06 16:52:36 EDT] read: git ["--git-dir=/srv/scratch/anarcat/isuma-annex-test/.git","--work-tree=/srv/scratch/anarcat/isuma-annex-test","log","refs/heads/git-annex..0ad850f59bdbe2448fa75e415ebfa5cf19cbebcd","-n1","--pretty=%H"]
[2015-04-06 16:52:36 EDT] read: git ["--git-dir=/srv/scratch/anarcat/isuma-annex-test/.git","--work-tree=/srv/scratch/anarcat/isuma-annex-test","log","refs/heads/git-annex..3476b0db2960fa9c9b00350e692e23dd30cd18c7","-n1","--pretty=%H"]
[2015-04-06 16:52:36 EDT] read: git ["--git-dir=/srv/scratch/anarcat/isuma-annex-test/.git","--work-tree=/srv/scratch/anarcat/isuma-annex-test","log","refs/heads/git-annex..d5cd95f472e00c51a2d35dedabf85f47cf3ce7fa","-n1","--pretty=%H"]
[2015-04-06 16:52:36 EDT] read: git ["--git-dir=/srv/scratch/anarcat/isuma-annex-test/.git","--work-tree=/srv/scratch/anarcat/isuma-annex-test","log","refs/heads/git-annex..778ba43445db7deb1bc6543e07145c13d3c3e5e2","-n1","--pretty=%H"]
[2015-04-06 16:52:36 EDT] chat: git ["--git-dir=/srv/scratch/anarcat/isuma-annex-test/.git","--work-tree=/srv/scratch/anarcat/isuma-annex-test","cat-file","--batch"]
[2015-04-06 16:52:36 EDT] read: git ["config","--null","--list"]
commit  [2015-04-06 16:52:36 EDT] read: git ["--git-dir=/srv/scratch/anarcat/isuma-annex-test/.git","--work-tree=/srv/scratch/anarcat/isuma-annex-test","commit","-a","-m","git-annex automatic sync"]
ok
[2015-04-06 16:52:36 EDT] read: git ["--git-dir=/srv/scratch/anarcat/isuma-annex-test/.git","--work-tree=/srv/scratch/anarcat/isuma-annex-test","symbolic-ref","HEAD"]
[2015-04-06 16:52:36 EDT] read: git ["--git-dir=/srv/scratch/anarcat/isuma-annex-test/.git","--work-tree=/srv/scratch/anarcat/isuma-annex-test","show-ref","refs/heads/master"]
[2015-04-06 16:52:36 EDT] call: git ["--git-dir=/srv/scratch/anarcat/isuma-annex-test/.git","--work-tree=/srv/scratch/anarcat/isuma-annex-test","show-ref","--verify","-q","refs/heads/synced/master"]
[2015-04-06 16:52:36 EDT] read: git ["--git-dir=/srv/scratch/anarcat/isuma-annex-test/.git","--work-tree=/srv/scratch/anarcat/isuma-annex-test","log","refs/heads/master..refs/heads/synced/master","-n1","--pretty=%H"]
pull test3
[2015-04-06 16:52:36 EDT] read: ssh ["-O","stop","-S","anarc.at","-o","ControlMaster=auto","-o","ControlPersist=yes","localhost"]
[2015-04-06 16:52:36 EDT] call: git ["--git-dir=/srv/scratch/anarcat/isuma-annex-test/.git","--work-tree=/srv/scratch/anarcat/isuma-annex-test","fetch","test3"]
git-annex: unknown command anarc.at
</pre>

Turning off `sshcaching` seems to work around the issue. Note that this happens even if the git repo is moved to a non-NFS filesystem, so I have the feeling it's not directly related to [this bugfix](http://source.git-annex.branchable.com/?p=source.git;a=commit;h=bd110516c09d318b298804efc4ee888270f3d601).

> [[done]]
