Merge methods

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

The examples on this page assume a main branch with commits A, C, and E, and a feature branch with commits B and D:

%%{init: { "fontFamily": "GitLab Sans" }}%% gitGraph accTitle: Diagram of a merge accDescr: A Git graph of five commits on two branches, which will be expanded on in other graphs in this page. commit id: "A" branch feature commit id: "B" commit id: "D" checkout main commit id: "C" commit id: "E"

Configure a project’s merge method

  1. On the left sidebar, select Search or go to and find your project.
  2. Select Settings > Merge requests.
  3. Select your desired Merge method from these options:
    • Merge commit
    • Merge commit with semi-linear history
    • Fast-forward merge
  4. In Squash commits when merging, select the default behavior for handling commits:
    • Do not allow: Squashing is never performed, and the user cannot change the behavior.
    • Allow: Squashing is off by default, but the user can change the behavior.
    • Encourage: Squashing is on by default, but the user can change the behavior.
    • Require: Squashing is always performed, and the user cannot change the behavior.
  5. Select Save changes.

Merge commit

By default, GitLab creates a merge commit when a branch is merged into main. A separate merge commit is always created, regardless of whether or not commits are squashed when merging. This strategy can result in both a squash commit and a merge commit being added to your main branch.

These diagrams show how the feature branch merges into main if you use the Merge commit strategy. They are equivalent to the command git merge --no-ff <feature>, and selecting Merge commit as the Merge method in the GitLab UI:

The merge strategy:

%%{init: { 'gitGraph': {'logLevel': 'debug', 'showBranches': true, 'showCommitLabel':true,'mainBranchName': 'main', 'fontFamily': 'GitLab Sans'}} }%% gitGraph accTitle: Diagram of a merge commit accDescr: A Git graph showing how merge commits are created in GitLab when a feature branch is merged. commit id: "A" branch feature commit id: "B" commit id: "D" checkout main commit id: "C" commit id: "E" merge feature

After a feature branch is merged with the Merge commit method, your main branch looks like this:

%%{init: { 'gitGraph': {'logLevel': 'debug', 'showBranches': true, 'showCommitLabel':true,'mainBranchName': 'main', 'fontFamily': 'GitLab Sans'}} }%% gitGraph accTitle: Diagram of the Merge Commit method accDescr: A Git graph showing the structure of a Git repository after a feature branch is merged. commit id: "A" commit id: "C" commit id: "E" commit id: "squash commit" commit id: "merge commit"

In comparison, a squash merge constructs a squash commit, a virtual copy of all commits from the feature branch. The original commits (B and D) remain unchanged on the feature branch, and the squash commit is placed on the main branch:

%%{init: { 'gitGraph': {'showBranches': true, 'showCommitLabel':true,'mainBranchName': 'main', 'fontFamily': 'GitLab Sans'}} }%% gitGraph accTitle: Diagram of of a squash merge accDescr: A Git graph showing repository and branch structure after a squash commit is added to the main branch. commit id:"A" branch feature checkout main commit id:"C" checkout feature commit id:"B" commit id:"D" checkout main commit id:"E" commit id:"squash commit" type: HIGHLIGHT

The squash merge graph is equivalent to these settings in the GitLab UI:

  • Merge method: Merge commit.
  • Squash commits when merging should be set to either:
    • Require.
    • Either Allow or Encourage, and squashing must be selected on the merge request.

The squash merge graph is also equivalent to these commands: 

  git checkout `git merge-base feature main`
  git merge --squash <feature>
  SOURCE_SHA=`git rev-parse HEAD`
  git checkout <main>
  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:

%%{init: { "fontFamily": "GitLab Sans" }}%% gitGraph accTitle: Diagram of a merge commit accDescr: Shows the flow of commits when a branch merges with a merge commit. 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:

%%{init: { "fontFamily": "GitLab Sans" }}%% gitGraph accTitle: Diagram of a fast-forward merge accDescr: Shows how a fast-forwarded merge request maintains a linear Git history, but does not add a merge commit. 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. 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 that use the fast-forward merge strategy can’t filter merge requests by deployment date, because no merge commit is created. Features that rely on the deployment-MR relationship do not work when fast-forward merges are enabled. This bug is tracked in issue 398611.

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 provides:

You must rebase the source branch locally before a fast-forward merge if both conditions are true:

  • The target branch is ahead of the source branch.
  • A conflict-free rebase is not possible.

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

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.
  • Not available when the Pipelines must succeed option is enabled.

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