Merge requests

Merge requests allow you to exchange changes you made to source code and collaborate with other people on the same project.

Overview

A Merge Request (MR) is the basis of GitLab as a code collaboration and version control platform. Is it simple as the name implies: a request to merge one branch into another.

With GitLab merge requests, you can:

Compare the changes between two branches
Review and discuss the proposed modifications inline
Live preview the changes when Review Apps is configured for your project
Build, test, and deploy your code in a per-branch basis with built-in GitLab CI/CD
Prevent the merge request from being merged before it's ready with WIP MRs
View the deployment process through Pipeline Graphs
Automatically close the issue(s) that originated the implementation proposed in the merge request
Assign it to any registered user, and change the assignee how many times you need
Assign a milestone and track the development of a broader implementation
Organize your issues and merge requests consistently throughout the project with labels
Add a time estimation and the time spent with that merge request with Time Tracking
Resolve merge conflicts from the UI
Enable fast-forward merge requests
Enable semi-linear history merge requests as another security layer to guarantee the pipeline is passing in the target branch

With GitLab Enterprise Edition, you can also:

View the deployment process across projects with Multi-Project Pipeline Graphs (available only in GitLab Enterprise Edition Premium)
Request approvals from your managers (available in GitLab Enterprise Edition Starter)
Squash and merge for a cleaner commit history (available in GitLab Enterprise Edition Starter)
Analise the impact of your changes with Code Quality reports (available in GitLab Enterprise Edition Starter)

Use cases

A. Consider you are a software developer working in a team:

You checkout a new branch, and submit your changes through a merge request
You gather feedback from your team
You work on the implementation optimizing code with Code Quality reports (available in GitLab Enterprise Edition Starter)
You build and test your changes with GitLab CI/CD
You request the approval from your manager
Your manager pushes a commit with his final review, approves the merge request, and set it to merge when pipeline succeeds (Merge Request Approvals are available in GitLab Enterprise Edition Starter)
Your changes get deployed to production with manual actions for GitLab CI/CD
Your implementations were successfully shipped to your customer

B. Consider you're a web developer writing a webpage for your company's:

You checkout a new branch, and submit a new page through a merge request
You gather feedback from your reviewers
Your changes are previewed with Review Apps
You request your web designers for their implementation
You request the approval from your manager (available in GitLab Enterprise Edition Starter)
Once approved, your merge request is squashed and merged, and deployed to staging with GitLab Pages (Squash and Merge is available in GitLab Enterprise Edition Starter)
Your production team cherry picks the merge commit into production

Merge requests per project

View all the merge requests within a project by navigating to Project > Merge Requests.

When you access your project's merge requests, GitLab will present them in a list, and you can use the tabs available to quickly filter by open and closed. You can also search and filter the results.

Merge requests per group

View all the merge requests in a group (that is, all the merge requests across all projects in that group) by navigating to Group > Merge Requests. This view also has the open, merged, and closed merge request tabs, from which you can search and filter the results.

Authorization for merge requests

There are two main ways to have a merge request flow with GitLab:

Working with protected branches in a single repository
Working with forks of an authoritative project

Learn more about the authorization for merge requests.

Cherry-pick changes

Cherry-pick any commit in the UI by simply clicking the Cherry-pick button in a merged merge requests or a commit.

Learn more about cherry-picking changes.

Semi-linear history merge requests

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 will also succeed after merging.

Navigate to a project's settings, select the Merge commit with semi-linear history option under Merge Requests: Merge method and save your changes.

Fast-forward merge requests

If you prefer a linear Git history and a way to accept merge requests without creating merge commits, you can configure this on a per-project basis.

Merge when pipeline succeeds

When reviewing a merge request that looks ready to merge but still has one or more CI jobs running, you can set it to be merged automatically when CI pipeline succeeds. This way, you don't have to wait for the pipeline to finish and remember to merge the request manually.

Learn more about merging when pipeline succeeds.

Resolve discussion comments in merge requests reviews

Keep track of the progress during a code review with resolving comments. Resolving comments prevents you from forgetting to address feedback and lets you hide discussions that are no longer relevant.

Resolve conflicts

When a merge request has conflicts, GitLab may provide the option to resolve those conflicts in the GitLab UI.

Learn more about resolving merge conflicts in the UI.

Revert changes

GitLab implements Git's powerful feature to revert any commit with introducing a Revert button in merge requests and commit details.

Learn more about reverting changes in the UI

Merge requests versions

Every time you push to a branch that is tied to a merge request, a new version of merge request diff is created. When you visit a merge request that contains more than one pushes, you can select and compare the versions of those merge request diffs.

Work In Progress merge requests

To prevent merge requests from accidentally being accepted before they're completely ready, GitLab blocks the "Accept" button for merge requests that have been marked as a Work In Progress.

Learn more about settings a merge request as "Work In Progress".

Merge request diff file navigation

The diff view has a persistent dropdown for file navigation. As you scroll through diffs with a large number of files and/or many changes in those files, you can easily jump to any changed file through the dropdown navigation.

Ignore whitespace changes in Merge Request diff view

If you click the Hide whitespace changes button, you can see the diff without whitespace changes (if there are any). This is also working when on a specific commit page.

Tip: You can append ?w=1 while on the diffs page of a merge request to ignore any whitespace changes.

Live preview with Review Apps

If you configured Review Apps for your project, you can preview the changes submitted to a feature-branch through a merge request in a per-branch basis. No need to checkout the branch, install and preview locally; all your changes will be available to preview by anyone with the Review Apps link.

Tips

Here are some tips that will help you be more efficient with merge requests in the command line.

Note: This section might move in its own document in the future.

Checkout merge requests locally

A merge request contains all the history from a repository, plus the additional commits added to the branch associated with the merge request. Here's a few tricks to checkout a merge request locally.

Please note that you can checkout a merge request locally even if the source project is a fork (even a private fork) of the target project.

Checkout locally by adding a git alias

Add the following alias to your ~/.gitconfig:

[alias]
    mr = !sh -c 'git fetch $1 merge-requests/$2/head:mr-$1-$2 && git checkout mr-$1-$2' -

Now you can check out a particular merge request from any repository and any remote. For example, to check out the merge request with ID 5 as shown in GitLab from the upstream remote, do:

git mr upstream 5

This will fetch the merge request into a local mr-upstream-5 branch and check it out.

Checkout locally by modifying `.git/config` for a given repository

Locate the section for your GitLab remote in the .git/config file. It looks like this:

[remote "origin"]
  url = https://gitlab.com/gitlab-org/gitlab-ce.git
  fetch = +refs/heads/*:refs/remotes/origin/*

You can open the file with:

git config -e

Now add the following line to the above section:

fetch = +refs/merge-requests/*/head:refs/remotes/origin/merge-requests/*

In the end, it should look like this:

[remote "origin"]
  url = https://gitlab.com/gitlab-org/gitlab-ce.git
  fetch = +refs/heads/*:refs/remotes/origin/*
  fetch = +refs/merge-requests/*/head:refs/remotes/origin/merge-requests/*

Now you can fetch all the merge requests:

git fetch origin

...
From https://gitlab.com/gitlab-org/gitlab-ce.git
 * [new ref]         refs/merge-requests/1/head -> origin/merge-requests/1
 * [new ref]         refs/merge-requests/2/head -> origin/merge-requests/2
...

And to check out a particular merge request:

git checkout origin/merge-requests/1