When you add the repository at ADMIN page did you switch the 'Methode' drop down menu from (Standard) to git? Added name and directory on the same line?
I'm also new to trac but my git repositories shows up.
I also don't have these lines in my trac.ini
[repository]
.type = git
.dir = /srv/git/gignore.git
I think the git repository is stored in ./db/trac.db instead.
I also discovered a message to add a hook to some git files to work properly. But I don't need to do this. Git integration works as expected.