use relative paths in config file

[dennisvang]

Use relative paths (i.e. relative to current working directory) for repo_dir and keys_dir in config file, if possible.
The config file itself is also in cwd.

Fixes #50

[dennisvang]

Hm... Looks like I'm running into something similar to actions/runner-images#712 again...

Windows truncates the username with a tilde (~1):

C:\Users\runneradmin\ becomes C:\Users\RUNNER~1\

but pathlib does not recognize that these are the same.

See 8.3 alias, this post, and wikipedia.

Looks like this is related: python/cpython#73181

Maybe this can resolve() the issue?

For example, instead of

self.assertEqual(path_a, path_b)

we would use

self.assertEqual(path_a.resolve(), path_b.resolve())

[dennisvang]

... and we appear to be running into python/cpython#82852 for python <3.10 on windows