Introduce a task to generate the announcement file for releases

[nicoddemus]

As discussed in the mailing list, introducing invoke tasks to simplify development and release process.

I started with a task to generate the AUTHORS file from git history but because pytest has a very old history, a lot of the names (60+) are not in a proper "name" format, a few examples:

famousgarkin
fijal
foxx
gabriel.reis
getxsick

I realized that finding the proper names would be a ton of work and not really worth the trouble, given that the AUTHORS file is updated during PRs and not during the release process.

This is the perfect place to introduce a task to update the CHANGELOG (#2390) IMO. 😁

[coveralls]

Coverage decreased (-0.1%) to 92.345% when pulling 66ba3c3 on nicoddemus:announce-task into daca618 on pytest-dev:features.

[RonnyPfannschmidt]

@nicoddemus can we introduce a git authormap that people may update at their leisure?

[nicoddemus]

can we introduce a git authormap that people may update at their leisure?

It is a possibility, but unfortunately I suspect a lot of people won't even be aware that their name now is incorrect in the AUTHORS file. Also I'm not sure this will gain us much because AUTHORS is updated during PRs, not during the release process, and PR contributors will also have to add a CHANGELOG entry anyway (even after introducing towncrier).

I thought about implementing a task that would only add new authors after a certain commit, so authors up until now would be preserved; but decided not to bother for the reasons stated above.

Regardless this topic is parallel to the task being introduced by this PR, which I find useful.

[nicoddemus]

Thanks @RonnyPfannschmidt