Merge methods

The merge method you select for your project determines how the changes in your merge requests are merged into an existing branch.

Configure a project’s merge method

  1. On the top bar, select Main menu > Projects and find your project.
  2. On the left sidebar, select Settings > Merge requests.
  3. In the Merge method section, select your desired merge method.
  4. Select Save changes.

Merge commit

This setting is the default. It always creates a separate merge commit, even when using squash. An example commit graph generated using this merge method:

gitGraph commit id: "Init" branch mr-branch-1 commit checkout main commit branch mr-branch-2 commit checkout mr-branch-1 commit checkout main branch squash-mr commit id: "Squashed commits" checkout main merge squash-mr merge mr-branch-1 commit merge mr-branch-2
  • For regular merges, it is equivalent to the command git merge --no-ff <source-branch>.
  • For squash merges, it squashes all commits in the source branch before merging it normally. It performs actions similar to:

    git checkout `git merge-base <source-branch> <target-branch>`
    git merge --squash <source-branch>
    SOURCE_SHA=`git rev-parse HEAD`
    git checkout <target-branch>
    git merge --no-ff $SOURCE_SHA
    

Merge commit with semi-linear history

A merge commit is created for every merge, but the branch is only merged if a fast-forward merge is possible. This ensures that if the merge request build succeeded, the target branch build also succeeds after the merge. An example commit graph generated using this merge method:

gitGraph commit id: "Init" branch mr-branch-1 commit commit checkout main merge mr-branch-1 branch mr-branch-2 commit commit checkout main merge mr-branch-2 commit branch squash-mr commit id: "Squashed commits" checkout main merge squash-mr

When you visit the merge request page with Merge commit with semi-linear history method selected, you can accept it only if a fast-forward merge is possible. When a fast-forward merge is not possible, the user is given the option to rebase, see Rebasing in (semi-)linear merge methods.

This method is equivalent to the same Git commands as in the Merge commit method. However, if your source branch is based on an out-of-date version of the target branch (such as main), you must rebase your source branch. This merge method creates a cleaner-looking history, while still enabling you to see where every branch began and was merged.

Fast-forward merge

Sometimes, a workflow policy might mandate a clean commit history without merge commits. In such cases, the fast-forward merge is appropriate. With fast-forward merge requests, you can retain a linear Git history and a way to accept merge requests without creating merge commits. An example commit graph generated using this merge method:

gitGraph commit id: "Init" commit id: "Merge mr-branch-1" commit id: "Merge mr-branch-2" commit id: "Commit on main" commit id: "Merge squash-mr"

This method is equivalent to git merge --ff <source-branch> for regular merges, and to git merge --squash <source-branch> for squash merges.

When the fast-forward merge (--ff-only) setting is enabled, no merge commits are created and all merges are fast-forwarded, which means that merging is only allowed if the branch can be fast-forwarded. When a fast-forward merge is not possible, the user is given the option to rebase, see Rebasing in (semi-)linear merge methods.

note
Projects using the fast-forward merge strategy can’t filter merge requests by deployment date, because no merge commit is created.

When you visit the merge request page with Fast-forward merge method selected, you can accept it only if a fast-forward merge is possible.

Fast-forward merge request

Rebasing in (semi-)linear merge methods

In these merge methods, you can merge only when your source branch is up-to-date with the target branch:

  • Merge commit with semi-linear history.
  • Fast-forward merge.

If a fast-forward merge is not possible but a conflict-free rebase is possible, GitLab offers you the /rebase quick action, and the ability to select Rebase from the user interface.

If the target branch is ahead of the source branch and a conflict-free rebase is not possible, you must rebase the source branch locally before you can do a fast-forward merge.

Fast forward merge rebase locally

Rebasing may be required before squashing, even though squashing can itself be considered equivalent to rebasing.

Rebase without CI/CD pipeline

Version history

To rebase a merge request’s branch without triggering a CI/CD pipeline, select Rebase without pipeline from the merge request reports section. This option is available when fast-forward merge is not possible but a conflict-free rebase is possible.

Rebasing without a CI/CD pipeline saves resources in projects with a semi-linear workflow that requires frequent rebases.