If you use the alternate form of ssh URLs you don’t need an absolute path. For example…
git clone lars@myserver.example.com:repos/myrepo.git
…will clone repository repos/myrepo.git relative to my home directory, although this doesn’t permit use of an alternate port. However, you can also use ~ in either form to indicate the user’s home directory, e.g.:
git clone ssh://login@server.com:12345/~/repository.git
Incidentally, despite being discontinued, gitosis functions quite well, and the code is both small and easy to understand. It offers a useful set of access controls and self-service management of repositories. I wouldn’t discount it completely.