First shot at removing usage of _markerlib and switching to the PEP 508 implementation in packaging.
Update to the newest packaging, and collapse _parse_requirement_specs
Experiment with using setuptools_scm for release management. This approach drastically simplifies the codebase, but imposes an initial dependency at install time, which could prove problemmatic in scenarios where connectivity is limited. This approach may not be viable for real-world consumption, but I'm committing it in this branch for consideration with no plans to release it without more testing and discussion.
Add tests capturing platform_python_implementation and implementation_version
Destroy MarkerEvaluation for being pointless, fix two silly mistakes in tests and update packaging changes.
Properly merge from default.
Shift packaging to use shiny extern.
This can be merged into the pr-164 bookmark, but sadly includes the first commit from that series because mercurial. I've also had to merge in setuptools-scm to even get this branch to push, so if I've done the wrong thing, let me know what to do to undo it.
This should hopefully sort out the major issues with pr-164. I'd like this to wait until packaging 15.4 is a released thing before this goes into a setuptools release.