Re-enable Cygwin CI and get most tests passing

[DWesl]

It looks like the Cygwin CI testing was disabled a while back, possibly as part of the move to GHA. I added a separate Cygwin CI run to the GitHub actions and tried to get the tests passing. I have three test failures left that I don't understand, and hope someone here knows what's going on.

I can move the test to a separate step in the existing GHA workflow if that would work better in this project, or move it to a separate PR to wait for the last three tests to pass while the other fixes go in.

[Byron]

Thanks a lot for putting in all this work and make GitPython work on cygwin once again.

Regarding the failing tests, I'd be OK with ignoring them if run on cygwin and providing a fix in other PRs. The failures are all related to submodule handling, and I think that functionality isn't necessarily widely used anymore.

[DWesl]

Regarding the failing tests, I'd be OK with ignoring them if run on cygwin and providing a fix in other PRs.

I got that done. Do you want to merge as-is, or do you want me to try to clean up the commits a bit?

The failures are all related to submodule handling, and I think that functionality isn't necessarily widely used anymore.

SciPy uses submodules to vendor boost, and I think both SciPy and NumPy include numpydoc via submodule. I haven't had any problems with the command-line interface (that can't be attributed to user error), but I only really use git submodule init and git submodule update.

[Byron]

I got that done. Do you want to merge as-is, or do you want me to try to clean up the commits a bit?

Thanks a lot! This looks good to me and I for one like to see all the steps it took in the history, thus I will merge as is.

SciPy uses submodules to vendor boost, and I think both SciPy and NumPy include numpydoc via submodule. I haven't had any problems with the command-line interface (that can't be attributed to user error), but I only really use git submodule init and git submodule update.

And for that, one could also use repo.git.submodule(…) to handle the necessary features, so I think it's not worth spending more time on fixing the tests (or their causes) unless you need it yourself.