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# Merge requests

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

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## 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](https://git-scm.com/book/en/v2/Git-Branching-Branches-in-a-Nutshell#_git_branching)
- [Review and discuss](../../discussions/index.md#discussions) the proposed modifications inline
- Live preview the changes when [Review Apps](../../../ci/review_apps/index.md) is configured for your project
- Build, test, and deploy your code in a per-branch basis with built-in [GitLab CI/CD](../../../ci/README.md)
- Prevent the merge request from being merged before it's ready with [WIP MRs](#work-in-progress-merge-requests)
- View the deployment process through [Pipeline Graphs](../../../ci/pipelines.md#pipeline-graphs)
- [Automatically close the issue(s)](../../project/issues/closing_issues.md#via-merge-request) 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](../../project/milestones/index.md) and track the development of a broader implementation
- Organize your issues and merge requests consistently throughout the project with [labels](../../project/labels.md)
- Add a time estimation and the time spent with that merge request with [Time Tracking](../../../workflow/time_tracking.html#time-tracking)
- [Resolve merge conflicts from the UI](#resolve-conflicts)

With **[GitLab Enterprise Edition][ee]**, you can also:

- View the deployment process across projects with [Multi-Project Pipeline Graphs](https://docs.gitlab.com/ee/ci/multi_project_pipeline_graphs.html#multi-project-pipeline-graphs) (available only in GitLab Enterprise Edition Premium)
- Request [approvals](https://docs.gitlab.com/ee/user/project/merge_requests/merge_request_approvals.html) from your managers (available in GitLab Enterprise Edition Starter)
- Enable [fast-forward merge requests](https://docs.gitlab.com/ee/user/project/merge_requests/fast_forward_merge.html) (available in GitLab Enterprise Edition Starter)
- [Squash and merge](https://docs.gitlab.com/ee/user/project/merge_requests/squash_and_merge.html) for a cleaner commit history (available in GitLab Enterprise Edition Starter)
- Enable [semi-linear history merge requests](https://docs.gitlab.com/ee/user/project/merge_requests/index.html#semi-linear-history-merge-requests) as another security layer to guarantee the pipeline is passing in the target branch (available in GitLab Enterprise Edition Starter)
- Analise the impact of your changes with [Code Quality reports](https://docs.gitlab.com/ee/user/project/merge_requests/code_quality_diff.html) (available in GitLab Enterprise Edition Starter)

## Use cases

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

1. You checkout a new branch, and submit your changes through a merge request
1. You gather feedback from your team
1. You work on the implementation optimizing code with [Code Quality reports](https://docs.gitlab.com/ee/user/project/merge_requests/code_quality_diff.html) (available in GitLab Enterprise Edition Starter)
1. You build and test your changes with GitLab CI/CD
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1. You request the approval from your manager
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1. Your manager pushes a commit with his final review, [approves the merge request](https://docs.gitlab.com/ee/user/project/merge_requests/merge_request_approvals.html), and set it to [merge when pipeline succeeds](#merge-when-pipeline-succeeds) (Merge Request Approvals are available in GitLab Enterprise Edition Starter)
1. Your changes get deployed to production with [manual actions](../../../ci/yaml/README.md#manual-actions) for GitLab CI/CD
1. Your implementations were successfully shipped to your customer

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

1. You checkout a new branch, and submit a new page through a merge request
1. You gather feedback from your reviewers
1. Your changes are previewed with [Review Apps](../../../ci/review_apps/index.md)
1. You request your web designers for their implementation
1. You request the [approval](https://docs.gitlab.com/ee/user/project/merge_requests/merge_request_approvals.html) from your manager (available in GitLab Enterprise Edition Starter)
1. Once approved, your merge request is [squashed and merged](https://docs.gitlab.com/ee/user/project/merge_requests/squash_and_merge.html), and [deployed to staging with GitLab Pages](https://about.gitlab.com/2016/08/26/ci-deployment-and-environments/) (Squash and Merge is available in GitLab Enterprise Edition Starter)
1. Your production team [cherry picks](#cherry-pick-changes) the merge commit into production

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## Authorization for merge requests

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

1. Working with [protected branches][] in a single repository
1. Working with forks of an authoritative project

[Learn more about the authorization for merge requests.](authorization_for_merge_requests.md)

## 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.](cherry_pick_changes.md)

## Merge when pipeline succeeds

When reviewing a merge request that looks ready to merge but still has one or
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more CI jobs running, you can set it to be merged automatically when CI
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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.](merge_when_pipeline_succeeds.md)

## 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.

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[Read more about resolving discussion comments in merge requests reviews.](../../discussions/index.md)
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## 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.](resolve_conflicts.md)

## 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](revert_changes.md)

## 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.

[Read more about the merge requests versions.](versions.md)

## 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".](work_in_progress_merge_requests.md)

## 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.

![MR diff](img/merge_request_diff.png)

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

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## Live preview with Review Apps

If you configured [Review Apps](https://about.gitlab.com/features/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.

[Read more about Review Apps.](../../../ci/review_apps/index.md)


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## 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
```

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[protected branches]: ../protected_branches.md
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[ee]: https://about.gitlab.com/gitlab-ee/ "GitLab Enterprise Edition"