Revert "Run git config instead of reading config file manually"

[straight-shoota]

The change is broken on Windows. This was masked by the CI failure due to #640.

E: Failed git config --get-regexp 'remote..+.mirror'.

Reverts #639

[beta-ziliani]

But why does that command fails? is that an issue with git?

[HertzDevil]

I think it would work on Windows if the single quotation marks are dropped

[straight-shoota]

It's documented behaviour of git config to exit with code 1 if "the section or key is invalid". Apparently --get-regexp considers a non-matching expression as an invalid key.

And the git behavious is not specific on Windows, it works the same on Linux (and I presume MacOS as well).
git config --get-regexp 'remote\..+\.mirror' on a repo with no matching remote in the config, exits with 1.

I just don't quite understand why this does not lead to a failure in shards on Linux and MacOS.