Automatically assign reviewers on pull request creation

[callmetango]

Describe the idea

We should automatically assign reviewers when a pull request gets created. At least in the Xserver repository.

The selection of the appropriate reviewers could be based on the path and/or extension of the source file. This is made possible by creating a CODEOWNERS file at the root of a repository. Also the selection could be based on some automatice rules defined at the organization and team level. We could also limit who is allowed to approve or request changes to a pull request.

An important note: "The people you choose as code owners must have write permissions for the repository", says the Github documentation. This can be generalized: Anyone who should be assignable as a reviewer needs write permissions for the repository.

It should be done because

Manually assigning reviewers to newly created pull requests is both tedious and errorprone. Without automation the devs have to manually select the reviews on a per pull request basis. Also any other contributor is not able to assign any reviewers, even not the core team ones so there may be no reviewers assigned after all and no notifications send etc. which can lead to stale pull requests.

When manually assigning reviewers one also has to know who reviews what and apply this knowledge to every new pull request. That way, essential reviewers might be forgotten. Also there may be no reviewers assigned at all as this is the Github default.

We should automatically assign the reviewers to get rid of the above mentioned shortcomings.

What are the alternatives?

Keep the status quo, but what for?

Additional context

This feature has been requested in various comments of pull requests when the (missing) workflow stood in the way of the ones working on the pull requests.

@X11Libre/wranglers CC

References to consider:

• About code owners - GitHub Docs
• Managing code review settings for your team - GitHub Docs
• Managing pull request reviews in your organization - GitHub Docs
• How automatically add a reviewer from a team when a PR is created? · community · Discussion #47988
• How do I make it so I can add my 8 team members as reviewers for my Pull Request easily? Can this be done automatically? · community · Discussion #57241

Extra fields

• I have checked the existing New Ideas, RFCs Of The Core Team, Ideas Soon To Be Addressed and Someday Ideas
• I have read the Contributing Guidelines
• I'd like to work on this idea

[callmetango]

This idea is to get things going, not a fleshed out solution.

IMO we should create a CODEOWNERS file in the XLibre Xserver repository at first and roll this out to all the other repositories once we are satified with the results. At the moment I wouldn't go for mutiple teams since the core team size is still manageable.

According to the documentation of the CODEOWNERS feature we can assign individuals or whole teams as default reviewers per path expression.

One thing to remember quoting the documentation:

The people you choose as code owners must have write permissions for the repository. When the code owner is a team, that team must be visible and it must have write permissions, even if all the individual members of the team already have write permissions directly, through organization membership, or through another team membership.