Allow tagging pre-release versions with ~ tilde character

[praiskup]

RPM and Deb distributions for some time allow to use ~suffix in software
pre-release versions (or distro releases). The benefit is that tagged
Version: 2~dev is obviously devel only version, but at the same time
users can rely on the fact that 2~dev < 2, in contrast to 2_dev > 2.

So maintainers can first bump to 2~dev and later "bump" to 2 only --
and still there's guaranteed upgrade path from pre-release to production
release.

It would be nice if tito allowed us to do

tito tag --use-version=something-with-tilde

The problem here is that git doesn't allow us to create tags with ~ in
name, that's because ~ has special meaning in git version jargon. So we
would have to have some clever version to tag and tag to version
translation. E.g.

tito tag --use-version=2~dev1

.. would create <name>-<version>_prerelease_dev1-<release> tag? Ideas?
Or s/~/@/?

[Conan-Kudo]

Using @ would be bad, since that has meaning in software ecosystems to be equivalent to =. I think a magic phrase would probably be better...

[xsuchy]

And

$ rpmdev-vercmp 1@1 1
1@git123 > 1

So proper tagged build will not upgrade test version. :(