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Merging Pull Requests

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Moritz Halbritter edited this page Feb 9, 2022 · 4 revisions

Fetching PRs

To ensure consistent and clean history, pull requests should never be merged using GitHub’s user interface. Instead you should always fetch a pull-request to your local machine to merge it.

Tip
 You can install this user-script in your browser to add manual merge steps to the GitHub UI

There are few ways to fetch PRs

Adding Remote Repos

If you have a regular contributor, you might want to add them as a remote repository so that you can easily fetch any branch that they create.

Do do this, you can use the following command:

$ git remote add example https://github.com/example/spring-boot

If you’re using Hub, this is even easier:

$ hub remote add example

In both cases, a new remote named example is created that points to https://github.com/example/spring-boot.

To check out the branch used for the pull request, creating a local branch named after the pull request as shown in the following example:

$ git checkout -b pr/1234 example/some-new-feature

The example above creates a local branch named pr/1234 that will track the some-new-feature branch of the example remote.

Fetching a Single PR

Adding a new remote for each pull-request can be annoying, so alternatively you can directly fetch a remote branch:

$ git fetch https://github.com/example/spring-boot.git some-new-feature
$ git checkout -b pr/1234 FETCH_HEAD

The example above creates a local branch named pr/1234 directly from the some-new-feature branch of the example remote.

With Hub, you can fetch the PR with one command:

$ hub pr checkout 1234 pr/1234

Or with GitHub CLI:

$ gh pr checkout 1234 -b pr/1234

Fetching All PRs

GitHub allows you to automatically fetch all pull-requests for a repository. To do this, you first have to edit the .git/config file for the repository.

Find the remote for the upstream project and add an additional pr/* section.

For example, if your remote is named spring-projects change this:

[remote "spring-projects"]
        url = https://github.com/spring-projects/spring-boot.git
        fetch = +refs/heads/*:refs/remotes/spring-projects/*

to this:

[remote "spring-projects"]
        url = https://github.com/spring-projects/spring-boot.git
        fetch = +refs/heads/*:refs/remotes/spring-projects/*
        fetch = +refs/pull/*/head:refs/remotes/spring-projects/pr/*

Now whenever you do git fetch <upstream> you’ll also get all pull-requests.

To checkout a pull request, you can do:

$ git checkout pr/15144

Rebasing PRs

Once you have fetched a PR locally, you’ll need to rebase it. First, fetch from <upstream> to ensure that you have an up-to-date via of the origin repository, as shown in the following example:

$ git fetch spring-projects

Rebase the branch on top of the branch into which it will be merged, as shown in the following example:

$ git rebase spring-projects/main
Tip
 Some users send multiple commits for a single pull request You can use git rebase -i spring-projects/main to do an interactive rebase. Use F to squash commits together

Fix any conflicts that result from the rebase and commit the changes.

Polishing PRs

Amend the commit message so that it matches the project’s style and references the pull request using See gh-1234 (not Closes gh-1234).

Make any changes that are necessary to polish the contributed code and commit them separately. The title of the polishing commit’s message should reference the title of the commit that’s being polished. For example, if the original commit’s title is Add support for some new feature the polishing commit’s title should be Polish "Add support for some new feature". Its message should also reference the pull request using See gh-1234.

Merging PRs

Check out the branch into which the changes will be merged, as shown in the following example:

$ git checkout main

Merge the changes. This should be done using --no-ff and --log to ensure that a fast-forward merge is not performed and to guarantee the creation of a useful merge commit. The merge commit makes merged pull requests easier to identify. The title of the merge commit should reference the pull request that’s being merged and the source of the pull request. It should also include "Closes gh-1234" so that the pull-request is closed. Here’s an example:

$ git merge --no-ff --log -m "Merge pull request #1234 from emmajones" pr/1234
$ git commit --amend -m"$(git log --format=%B -n1)$(echo -e "\n\nCloses gh-1234")"

If you merge a lot of PRs you can optionally use this alias and then type:

$ git mergepr pr/1234

The example above merges the branch pr/1234. The title of the merge commit will be:

Merge pull request #1234 from emmajones

* gh-17002:
  Check for null in SpringApplication constructor
  Polish "Check for null in SpringApplication constructor"

Closes gh-1234

The changes can now be pushed and your local workspace tidied up by deleting your local branch and the remote (if used), as shown in the following example:

$ git branch -d pr/1234
$ git remote remove example

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