Support processing the commits starting from a specific tag

Is there an existing issue or pull request for this?

• I have searched the existing issues and pull requests

Feature description

Currently, there's support for processing commits starting from the current or latest tag, or commits without any tag, but not starting from a specific tag. This would make the transition from unconventional commits to conventional commits much smoother. Then, you could keep the old changelog as, e.g. HISTORY.md, and then start a new CHANGELOG.md based on commits after a specific tag.

Desired solution

Introduce a new command-line argument that can be used to specify the tag that should be used to start fetching commits from.

Alternatives considered

Can't think of any.

Additional context

No response