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Article version: Enterprise Server 2.18

About pull request merges

You can merge pull requests by retaining all the commits in a feature branch, squashing all commits into a single commit, or by rebasing individual commits from the head branch onto the base branch.

In this article

When you click the default Merge pull request option on a pull request on your GitHub Enterprise Server instance, all commits from the feature branch are added to the base branch in a merge commit. The pull request is merged using the --no-ff option.

To merge pull requests, you must have write permissions in the repository.

standard-merge-commit-diagram

Squash and merge your pull request commits

When you select the Squash and merge option on a pull request on your GitHub Enterprise Server instance, the pull request's commits are squashed into a single commit. Instead of seeing all of a contributor's individual commits from a topic branch, the commits are combined into one commit and merged into the default branch. Pull requests with squashed commits are merged using the fast-forward option.

To squash and merge pull requests, you must have write permissions in the repository, and the repository must allow squash merging.

commit-squashing-diagram

You can use squash and merge to create a more streamlined Git history in your repository. Work-in-progress commits are helpful when working on a feature branch, but they aren’t necessarily important to retain in the Git history. If you squash these commits into one commit while merging to the default branch, you can retain the original changes with a clear Git history.

Merge message for a squash merge

When you squash and merge, GitHub generates a commit message which you can change if you want to. The message default depends on whether the pull request contains multiple commits or just one.

Number of commitsSummaryDescription
One commitThe title of the commit message for the single commit, followed by the pull request numberThe body text of the commit message for the single commit
More than one commitThe pull request title, followed by the pull request numberA list of the commit messages for all of the squashed commits, in date order

Squashing and merging a long-running branch

If you plan to continue work on the head branch of a pull request after the pull request is merged, we recommend you don't squash and merge the pull request.

When you create a pull request, GitHub identifies the most recent commit that is on both the head branch and the base branch: the common ancestor commit. When you squash and merge the pull request, GitHub creates a commit on the base branch that contains all of the changes you made on the head branch since the common ancestor commit.

Because this commit is only on the base branch and not the head branch, the common ancestor of the two branches remains unchanged. If you continue to work on the head branch, then create a new pull request between the two branches, the pull request will include all of the commits since the common ancestor, including commits that you squashed and merged in the previous pull request. If there are no conflicts, you can safely merge these commits. However, this workflow makes merge conflicts more likely. If you continue to squash and merge pull requests for a long-running head branch, you will have to resolve the same conflicts repeatedly.

Rebase and merge your pull request commits

When you select the Rebase and merge option on a pull request on your GitHub Enterprise Server instance, all commits from the topic branch (or head branch) are added onto the base branch individually without a merge commit. Pull requests with rebased commits are merged using the fast-forward option.

To rebase and merge pull requests, you must have write permissions in the repository, and the repository must allow rebase merging.

The rebase and merge behavior on GitHub Enterprise deviates slightly from git rebase. Rebase and merge on GitHub will always update the committer information and create new commit SHAs, whereas git rebase outside of GitHub does not change the committer information when the rebase happens on top of an ancestor commit. For more information about git rebase, see the "Git rebase" chapter from the Pro Git book.

For a visual representation of git rebase, see The "Git Branching - Rebasing" chapter from the Pro Git book.

You aren't able to automatically rebase and merge on your GitHub Enterprise Server instance when:

  • The pull request has merge conflicts.
  • Rebasing the commits from the base branch into the head branch runs into conflicts.
  • Rebasing the commits is considered "unsafe," such as when a rebase is possible without merge conflicts but would produce a different result than a merge would.

If you still want to rebase the commits but can't rebase and merge automatically on your GitHub Enterprise Server instance you must:

Anyone with write permissions in the repository, can then merge the changes using the rebase and merge button on your GitHub Enterprise Server instance.

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