Support bare repositories

[SlugFiller]

Is your feature request related to a problem? Please describe.
Trying to import a bare repository fails, because the .git folder is not present, and it is not attempting to look for Git files in the current directory. Instead, you just get a toast saying there's no repository in that path.

Describe the solution you'd like
I'd like for the repository to open in read-only mode. i.e. It's not possible to commit to it (since no working directory), but it should still be possible to browse the revisions, and open a file from any given revision.