Create changelog from merge commits

[feelepxyz]

Build the changelog entries from merge commit PR details instead of the individual commits, automating attribution to non-team members and including a link to the PR.

Example:

## v0.146.0, 5 May 2021

- fix(Go mod): detect when remote end hangs up [#3469](https://github.com/dependabot/dependabot-core/pull/3469)
- Final pass on bundler1 test cruft [#3466](https://github.com/dependabot/dependabot-core/pull/3466)
- Handle repo not found errors for go modules [#3456](https://github.com/dependabot/dependabot-core/pull/3456)
- Disabled poetry experimental new installer (@honnix) [#3459](https://github.com/dependabot/dependabot-core/pull/3459)
- Implement delete/create action in GitLab Client (@jerbob92) [#3414](https://github.com/dependabot/dependabot-core/pull/3414)

[thepwagner]

wanted to get feedback on the idea of using gh to do this,

👍

This (PR titles) is what I tend to do manually when I'm not familiar enough with a diff to summarize.

Aside: https://github.com/atlassian/changesets / https://github.com/changesets/action provides some neat tooling here too, but that's a much bigger leap than "CHANGELOG.md, but easier".

---

Alternatively, what about a process that encourages CHANGELOG.md be modified as part of each PR? That solves the summarization problem, and lets contributors decide themselves if they want a shoutout, etc...

Meh, that's manual and tedious - this is ✨magic✨ .

[feelepxyz]

Aside: https://github.com/atlassian/changesets / https://github.com/changesets/action provides some neat tooling here too, but that's a much bigger leap than "CHANGELOG.md, but easier".

This looks cool! Up for testing it out.

Yeah keen to improve the current flow a bit as I frequently reach for the PRs to reach for author/title.

[jurre]

I dig it!

[brrygrdn]

👍🏻 I like this approach, as _thepwagner notes this is automating what I already do when I don't have context on the change. I think it's a good forcing function to encourage expressive Pull Request naming by authors and their reviewers over time.

[Nishnha]

nit typo for exit

[feelepxyz]

nice catch!