Add the ability to additionally add the changelog to a separate file like CHANGELOG.md

[ryan-blakley]

It would be nice to have the ability to append the changelog to an external file like a CHANGELOG.md file. Also possibly add the ability to add a jinja template for the external file, since most external changelog files are md or rst files.

[FrostyX]

Hello @ryan-blakley, that is indeed a good idea.

Tito can already generate files from templates when tagging a new version. There is not much documentation for it but it is mentioned for example here https://docs.fedoraproject.org/en-US/quick-docs/publish-rpm-on-copr/#_step_4_let_tito_manage_the_program_version and in this repository, we use it to generate src/tito/__init__.py. At this moment, only $version and $release variables can be substituted in the template but we could support $changelog as well. Would this work for you?

Also possibly add the ability to add a jinja template

Jinja2 would be my preferred templating engine but since we already support templates, migrating to Jinja2 is a lower priority for me (unless there is some use case that requires it)

since most external changelog files are md or rst files.

The main problem I see is what should be the format of the changelog? There isn't going to be anything compatible across all the markup languages, so I suppose we would have to somehow let users define their custom format. What are your thoughts on this?