Improve release process: Update CHANGELOG in every PR

[Ana06]

Instead of having to go over all commits when we release, I suggest we update the CHANGELOG in every PR. Two things are needed to put this in practice:

1. CHANGELOG template.
2. GitHub Action to enforce this is used. A check in PR will fail if the CHANGELOG is not modified and the no changelog (or similar name) tag is not used.
3. Update documentation
4. [OPTIONAL] Create a PR template (as with issues to remind about this and link the documentation)

My only concern about this approach are the merge conflicts in the CHANGELOG file. But we could try it and adapt the process if it doesn't work.

Advantages:

• capa users can see what changes they might expect in upcoming releases
• The author of a change is the person who know the change the best and consequently the one who can write the best CHANGELOG entry
• Make releasing easier and less time consuming, as just some small modifications are needed to the CHANGELOG to be able to release. To achieve this we invest a bit more time in every PR to document changes, but I think it requires less time to document something when you do it than after some days/weeks.

This may be useful: https://keepachangelog.com/en/1.0.0

What do you think? Should we give it a try?

[Ana06]

This wouldn't include the rules as they are in a different repo, but the new rules could maybe be automatized with Github Actions once this is setup.

[williballenthin]

if you can create and maintain the gh action, i'm ok going forward with this plan.

i like the idea of having a PR template with the changelog details, too.

[Ana06]

GitHub Action to enforce this is used. A check in PR will fail if the CHANGELOG is not modified and the no changelog (or similar name) tag is not used.

I have a good solution for this: request changes in a PR if the CHANGELOG hasn't been updated and the text No CHANGELOG update needed is not in the PR description with GitHub actions. If the CHANGELOG or the PR description is updated to meet the requirements, then the changes request is dimissed with GitHub actions). But I need to modify/fix https://github.com/AndrewMusgrave/automatic-pull-request-review and https://github.com/jitterbit/get-changed-files for it to work. I have submitted issues/PR and I am waiting for their input.

You can see the requests changes part working here: Ana06#28
The needed changes are in https://github.com/Ana06/capa/commits/master (they are using https://github.com/Ana06/automatic-pull-request-review and https://github.com/Ana06/get-changed-files, I have submitted those changes upstream).