hghave: document format for version feature checks as <name><vers>, no dots I had a bit of a difficult time when attempting to fix a use of `py-38` when trying to figure out what the correct way of specifying the feature was. By having the strings 'py-3*' and 'py3.8' in the hghave.checkvers docstring, I would have had a much easier time of it instead of having to trace exactly what was happening here. Differential Revision: https://phab.mercurial-scm.org/D7023