Make substitutions available to lifecycle scripts

[esciara]

This is close to #283, but wider. Is it possible to make substitutions available to the lifecycle scripts?

I am stuck at the moment because I cannot run scripts that would need to know the {{previousTag}} and {{currentTag}}, like in the following example:

{
  "scripts": {
    "postbump": "bump2version --current-version {{previousTag}} --new-version {{currentTag}}"
  }
}

[esciara]

Note: after more digging, my specific example would be solved by resolving #313, which is the aim of #372 . Not sure whether making substitutions available would solve other situations...

[tim-felix-lange]

Would definitely be interested in this feature as well for various use cases, like creating version-specific release branches in precommit scripts, etc.