Run Onefetch in any of the repo's subfolders

[o2sh]

As suggested by @davep in #100 , It would be handy if the tool could work anywhere within a git repo, rather than only in the root of the repo.

The idea would be to search for the .git folder in any of the parent directories as a marker for the root of the repo and to execute onefetch on it 👍

If it fails to find it, the error message should be:

fatal: not a git repository (or any of the parent directories): .git

[spenserblack]

Considering git -C path/to/repo/subfolder/ <git command> works fine, this could also be solved by switching git2::Repository usage with std::process::Command usage.

[rockisch]

Seems like the git2 package supports this kind of usage with the discover method:
https://docs.rs/git2/0.10.1/git2/struct.Repository.html#method.discover

I'm opening a PR for that, although not sure I should use the error message on the description, since that's not how the other error messages are formatted.

[spenserblack]

Closed by #132
Thanks, @rockisch!

[o2sh]

The function get_project_license doesn't work in subfolders

[rockisch]

Damn, I ran a little test but didn't check the individual fields, my bad.

I think git2::Repository has some kind of method to get the root dir of the repo. I can check later when I'm home.

[davep]

Updated locally and it's working great. Just wanted to say thanks for doing this. Very much appreciated.