bug#60725: guix lint thinks 2019111-0.7e76d75 is older than 20191111

[Maxim Cournoyer]

Hi Guix,

If you run 'guix lint emacs-enh-ruby-mode', it'll print this:

--8<---------------cut here---------------start------------->8---
emacs-enh-ruby-mode@2019111-0.7e76d75: can be upgraded to 20191111
--8<---------------cut here---------------end--------------->8---

That's wrong; it should know that something that starts with the tag and
has trailing characters is considered newer.  Actually, it should
probably implement the RPM scheme used in Debian also, so that an RC can
be understood as older than the final release.  The scheme uses the
tilde character (~) as a way to specify that the version is lower than
the number that precedes the tilde.

See the test case here for a "specification" (there may be a better
place):
https://github.com/rpm-software-management/rpm/blob/4afe2d14d33db82ccb41c0a8d5eb1a4db90762fc/tests/rpmvercmp.at#L94

-- 
Thanks,
Maxim