Version constraining to even/odd versions

[darkdragon-001]

Some packages use even/odd versioning for stable/unstable version numbers (see Wikipedia). It would be nice if one could restrain versions in such a way that only stable numbers are proposed.

[wjt]

The GNOME checker supports GNOME's (previous) similar scheme. It does seem a reasonable addition elsewhere.

In the linked case of Calls you could fake it with:

        x-checker-data:
          type: git
          #version-scheme: semantic
          tag-pattern: ^(\d+\.\d*[02468]\.\d+)$

[bbhtt]

In majority of the checkers this can be done by modifying the pattern regexps directly and for checkers where that doesn't exist, they support stable-only. Even/odd restrictions make sense to only filter to stable releases.

It's not clear why something new needs to be added here. The regexes already allow greater control.