Tag prefix broken on Windows with versioneer 0.21

https://github.com/python-versioneer/python-versioneer/pull/262 contains a fix for handling * on windows unfortunately this breaks detecting the correct version for me.

In our repository https://github.com/qcodes/qcodes all tags are prefixed with v and we have tag_prefix = v this used to work fine however with the latest release of versioneer we get versions reported as unknown + x

Looking at the generated git describe command we see

git describe --tags --always --long --dirty --match v*
v0.29.0-288-g9f93a1286

git describe --tags --always --long --dirty --match v\*
9f93a1286

git describe --tags --always --long --dirty --match v\\*
9f93a1286

so it would seem like the escape of * does not always work correctly. removing the escaped prefix for windows restores normal functionality for us

[mathijsvdv]

@hwjohn I’ll take that into account and also see if the tag prefix works consistently on all platforms if it is provided.

[hwjohn]

@mathijsvdv , I would be grateful if you provided a fix.

I think a better solution than what is currently implemented in #274 is to just omit the --match option entirely from the git command if there is no tag prefix. This will avoid any issues with trying to predict the correct escape sequence for a given platform.