# Merging changes in Coq This document describes how patches (submitted as pull requests on the `master` branch) should be merged into the main repository (https://github.com/coq/coq). ## Code owners The [CODEOWNERS](/.github/CODEOWNERS) file describes, for each part of the system, two owners. One is the principal maintainer of the component, the other is the secondary maintainer. When a pull request is submitted, GitHub will automatically ask the principal maintainer for a review. If the pull request touches several parts, all the corresponding principal maintainers will be asked for a review. Maintainers are never assigned as reviewer on their own PRs. If a principal maintainer submits a PR that changes the component they own, they must assign the secondary maintainer as reviewer. They should also do it if they know they are not available to do the review. ## Reviewing When maintainers receive a review request, they are expected to: * Put their name in the assignee field, if they are in charge of the component that is the main target of the patch (or if they are the only maintainer asked to review the PR). * Review the PR, approve it or request changes. * If they are the assignee, check if all reviewers approved the PR. If not, regularly ping the author (if changes should be implemented) or the reviewers (if reviews are missing). The assignee ensures that any requests for more discussion have been granted. When the discussion has converged and ALL REVIEWERS(*) have approved the PR, the assignee is expected to follow the merging process described below. In all cases, maintainers can delegate reviews to the other maintainer of the same component, except if it would lead to a maintainer reviewing their own patch. A maintainer is expected to be reasonably reactive, but no specific timeframe is given for reviewing. (*) In case a component is touched in a trivial way (adding/removing one file in a `Makefile`, etc), or by applying a systematic process (global renaming, deprecationg propagation, etc) that has been reviewed globally, the assignee can say in a comment they think a review is not required and proceed with the merge. ## Merging Once all reviewers approved the PR, the assignee is expected to check that CI completed without relevant failures, and that the PR comes with appropriate documentation and test cases. If not, they should leave a comment on the PR and put the approriate label. Otherwise, they are expected to merge the PR using the [merge script](/dev/tools/merge-pr.sh). When the PR has conflicts, the assignee can either: - ask the author to rebase the branch, fixing the conflicts - warn the author that they are going to rebase the branch, and push to the branch directly In both cases, CI should be run again. In some rare cases (e.g. the conflicts are in the CHANGES file), it is ok to fix the conflicts in the merge commit (following the same steps as below), and push to `master` directly. Don't use the GitHub interface to fix these conflicts. To merge the PR proceed in the following way ``` $ git checkout master $ git pull $ dev/tools/merge-pr XXXX $ git push upstream ``` where `XXXX` is the number of the PR to be merged and `upstream` is the name of your remote pointing to `git@github.com:coq/coq.git`. Note that you are only supposed to merge PRs into `master`. PRs should rarely target the stable branch, but when it is the case they are the responsibility of the release manager. This script conducts various checks before proceeding to merge. Don't bypass them without a good reason to, and in that case, write a comment in the PR thread to explain the reason. Maintainers MUST NOT merge their own patches. DON'T USE the GitHub interface for merging, since it will prevent the automated backport script from operating properly, generates bad commit messages, and a messy history when there are conflicts. ### What to do if the PR has overlays If the PR breaks compatibility of some developments in CI, then the author must have prepared overlays for these developments (see [`dev/ci/README.md`](/dev/ci/README.md)) and the PR must absolutely update the `CHANGES` file. There are two cases to consider: - If the patch is backward compatible (best scenario), then you should get upstream maintainers to integrate it before merging the PR. - If the patch is not backward compatible (which is often the case when patching plugins after an update to the Coq API), then you can proceed to merge the PR and then notify upstream they can merge the patch. This is a less preferable scenario because it is probably going to create spurious CI failures for unrelated PRs. ### Merge script dependencies The merge script passes option `-S` to `git merge` to ensure merge commits are signed. Consequently, it depends on the GnuPG command utility being installed and a GPG key being available. Here is a short tutorial to creating your own GPG key: The script depends on a few other utilities. If you are a Nix user, the simplest way of getting them is to run `nix-shell` first. **Note for homebrew (MacOS) users:** it has been reported that installing GnuPG is not out of the box. Installing explicitly "pinentry-mac" seems important for typing of passphrase to work correctly (see also this [Stack Overflow Q-and-A](https://stackoverflow.com/questions/39494631/gpg-failed-to-sign-the-data-fatal-failed-to-write-commit-object-git-2-10-0)).