New feature: being able to extract and inject part of existing changelog files to the release body

[Eloy Lafuente]

Is your feature request related to a problem? Please describe.
Not a big problem, other actions provide that, but I think it may have sense to implement it straight into this action, hence, sharing.

Similarly to the current feature that allows the action to fill the release notes from GH release API automatically, it would be great if the actions was able to extract the release notes from a manually/custom/other sytem maintained CHANGELOG.md file.

Describe the solution you'd like
Basically, if a path to a changelog file is specified, and if the changelog file is correctly structured, then the information will be extracted from that file (for the version being released) and injected into the "body", surely at the very beginning by default but, if some {{PUT_CHANGELOG_HERE}} (template-like) is detected in the body, then the information should go there.

Describe alternatives you've considered
As said, I'm using other actions or custom scripts to perform the extraction from different changelogs or other systems and then, adding them to your action adding outputs from other steps to the body.

Just thought that, maybe, the use case (having a wellformed changelog file in the repo) is frequent enough to consider supporting it from within the action.

Additional context
Ciao :-)

[Nick Cipollo]

Thanks for the suggestion!

While I think this is a good usecase, I want to keep the scope of this action focused around the management of the release itself. As you mention there are other actions which can be used to generate the body from a change log file, etc. I think keeping this functionality separate from the release generation offers the greatest flexibility since you can chose from a variety of approaches within the workflow itself.