What steps will reproduce the problem?
1. Create a Repository
2. Add a Remote Server

What is the expected output? What do you see instead?
The option "Use a git repository on the server" is marked as not available

What version of git-annex are you using? On what operating system?
Version: 4.20130405 but on Webapp ist shows: Version: 4.20130324
Linux 64bit

Please provide any additional information below.
git and git-annex are available on the Remote Server

> While this bug report was about a server that did not get git-annex-shell
> installed in PATH (something trivially fixed by `apt-get install
> git-annex`), the comments below would like to turn this into a bug report about 
> the error message "unknown UUID; cannot modify". All right then..
> --[[Joey]]
> 
> This can occur if a ssh key is locked down to use directory A, and a
> new repo is added in directory B which uses the same ssh key. Things will
> then fail when git-annex-shell rejects the attept to use directory B, and
> this results in the webapp displaying an internal server error of
> "unknown UUID; cannot modify" since NoUUID is retreived for the repo.
> 
> In fact, I already dealt with this
> once in 79561774450c8abf7c2cb42b08575a3ca27010dc; it used to not use 
> the directory name at all as part of the mangled hostname. Most of the 
> "me too" responses" predate that fix.
> 
> Now, this can only happen
> if the mangled hostname for directory A and B is the same. One way this can
> happen is if the directories are "annex" and "~/annex". In other words,
> I suspect that users are entering "annex" once, and "~/annex" another
> time, when setting up what they intend to be the same repo. Perhaps the
> first time something else fails (like the original problem of
> git-annex-shell not being in path), or they want to set it up again,
> and the next time the subtly different directory is entered.
> 
> To fix this,
> `mangleSshHostName` would need to be changed to generate different mangled
> hostnames in all cases. Currently, it skips non-alpha-numeric
> characters in the directory. [[done]] --[[Joey]]
> --[[Joey]] 
> 
> Additionally, just entering a path starting with "~/" would cause this
> error, since the webapp tacks on "/~/" to make a relative path absolute.
> I've also fixed that. [[done]] --[[Joey]]