Description

This PR adds a semver2 version scheme which is applying strict prerelease formatting as described in SemVer 2 Item 9 and Semver 2.0.0 Item 11, meaning:

• each prelease identifier should be separated by a dot
• dash is part of the identifier, not a separator
• precedence rules should be applied on identifiers

As a consequence, the 1.2.3-alpha0 form is not respecting those rules (1.2.3-alpha10 has not proper precedence over 1.2.3-alpha2), nor 1.2.3-alpha.0-dev.0 as its prerelease identifiers will be alpha, 0-dev, 0 while it should be alpha, 0, dev and 0.

Note that Semver 2 is underspecified on this point (there is no formal description of what are the expected prerelease identifiers, only example) and so this PR chose to stay close to the examples (use of alpha and beta instead of a and b), but this is choice, not a specification requirement.

Checklist

• Add test cases to all the changes you introduce
• Run ./scripts/format and ./scripts/test locally to ensure this change passes linter check and test
• Test the changes on the local machine manually
• Update the documentation for the changes

Expected behavior

SemVer 2.0 versions are properly parsed and bumped, the resulting version is SemVer 2,0 compliant too.

Steps to Test This Pull Request

1. Defined version_scheme = "semver2" in you commitizen config
2. Bump a dev release, it should have the form x.y.z-dev.D
3. Bump an alpha release, it should have the form x.y.z-alpha.A
4. Bump an alpha dev release, it should have the form x.y.z-alpha.A.dev.D

Additional context

Fixes #1025