# Merge requests

We welcome merge requests from everyone, with fixes and improvements
to GitLab code, tests, and documentation. The issues that are specifically suitable
for community contributions are listed with the [`Accepting merge requests`](issue_workflow.md#label-for-community-contributors)
label, but you are free to contribute to any issue you want.

Please note that if an issue is marked for the current milestone at any time, even
when you are working on it, a GitLab Inc. team member may take over the merge request
in order to ensure the work is finished before the release date.

If you want to add a new feature that is not labeled, it is best to first create
an issue (if there isn't one already) and leave a comment asking for it
to be marked as `Accepting Merge Requests`. Please include screenshots or
wireframes of the proposed feature if it will also change the UI.

Merge requests should be submitted to the appropriate project at GitLab.com, for example
[GitLab CE](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests),
[GitLab EE](https://gitlab.com/gitlab-org/gitlab-ee/merge_requests),
[GitLab Runner](https://gitlab.com/gitlab-org/gitlab-runner/merge_requests),
[GitLab Omnibus](https://gitlab.com/gitlab-org/omnibus-gitlab/merge_requests), etc.

If you are new to GitLab development (or web development in general), see the
[I want to contribute!](index.md#i-want-to-contribute) section to get started with
some potentially easy issues.

To start developing GitLab, download the [GitLab Development Kit](https://gitlab.com/gitlab-org/gitlab-development-kit)
and see the [Development section](../../README.md) for the required guidelines.

## Merge request guidelines

If you find an issue, please submit a merge request with a fix or improvement, if
you can, and include tests. If you don't know how to fix the issue but can write a test
that exposes the issue, we will accept that as well. In general, bug fixes that
include a regression test are merged quickly, while new features without proper
tests might be slower to receive feedback. The workflow to make a merge
request is as follows:

1. [Fork](../../workflow/forking_workflow.md#creating-a-fork) the project into
   your personal namespace (or group) on GitLab.com.
1. Create a feature branch in your fork (don't work off `master`).
1. Write [tests](../rake_tasks.md#run-tests) and code.
1. [Generate a changelog entry with `bin/changelog`](../changelog.md)
1. If you are writing documentation, make sure to follow the
   [documentation guidelines](../documentation/index.md).
1. Follow the [commit messages guidelines](#commit-messages-guidelines).
1. If you have multiple commits, combine them into a few logically organized
   commits by [squashing them](https://git-scm.com/book/en/v2/Git-Tools-Rewriting-History#_squashing),
   but do not change the commit history if you're working on shared branches though.
1. Push the commit(s) to your working branch in your fork.
1. Submit a merge request (MR) to the `master` branch in the main GitLab project.
   1. Your merge request needs at least 1 approval, but feel free to require more.
      For instance if you're touching both backend and frontend code, it's a good idea
      to require 2 approvals: 1 from a backend maintainer and 1 from a frontend
      maintainer.
   1. If you're submitting changes to documentation, you'll need approval from a technical
      writer, based on the appropriate [product category](https://about.gitlab.com/handbook/product/categories/).
      Only assign the MR to them when it's ready for docs review.
   1. You don't have to select any specific approvers, but you can if you really want
      specific people to approve your merge request.
1. The MR title should describe the change you want to make.
1. The MR description should give a reason for your change.
   1. If you are contributing code, fill in the description according to the default
      template already provided in the "Description" field.
   1. If you are contributing documentation, choose `Documentation` from the
      "Choose a template" menu and fill in the description according to the template.
   1. Mention the issue(s) your merge request solves, using the `Solves #XXX` or
      `Closes #XXX` syntax to [auto-close](../../user/project/issues/managing_issues.md#closing-issues-automatically)
      the issue(s) once the merge request is merged.
1. If you're allowed to (Core team members, for example), set a relevant milestone
   and [labels](issue_workflow.md).
1. If the MR changes the UI, it should include *Before* and *After* screenshots.
1. If the MR changes CSS classes, please include the list of affected pages, which
   can be found by running `grep css-class ./app -R`.
1. Be prepared to answer questions and incorporate feedback into your MR with new
   commits. Once you have fully addressed a suggestion from a reviewer, click the
   "Resolve thread" button beneath it to mark it resolved.
   1. The merge request author resolves only the threads they have fully addressed.
      If there's an open reply or thread, a suggestion, a question, or anything else,
      the thread should be left to be resolved by the reviewer.
1. If your MR touches code that executes shell commands, reads or opens files, or
   handles paths to files on disk, make sure it adheres to the
   [shell command guidelines](../shell_commands.md)
1. If your code creates new files on disk please read the
   [shared files guidelines](../shared_files.md).
1. If your merge request adds one or more migrations, make sure to execute all
   migrations on a fresh database before the MR is reviewed. If the review leads
   to large changes in the MR, execute the migrations again once the review is complete.
1. Write tests for more complex migrations.
1. Merge requests **must** adhere to the [merge request performance guidelines](../merge_request_performance_guidelines.md).
1. For tests that use Capybara, read
   [how to write reliable, asynchronous integration tests](https://robots.thoughtbot.com/write-reliable-asynchronous-integration-tests-with-capybara).
1. If your merge request introduces changes that require additional steps when
   installing GitLab from source, add them to `doc/install/installation.md` in
   the same merge request.
1. If your merge request introduces changes that require additional steps when
   upgrading GitLab from source, add them to
   `doc/update/upgrading_from_source.md` in the same merge request. If these
   instructions are specific to a version, add them to the "Version specific
   upgrading instructions" section.

If you would like quick feedback on your merge request feel free to mention someone
from the [core team](https://about.gitlab.com/community/core-team/) or one of the
[merge request coaches](https://about.gitlab.com/team/). When having your code reviewed
and when reviewing merge requests, please keep the [code review guidelines](../code_review.md)
in mind. And if your code also makes changes to the database, or does expensive queries,
check the [database review guidelines](../database_review.md).

### Keep it simple

*Live by smaller iterations.* Please keep the amount of changes in a single MR **as small as possible**.
If you want to contribute a large feature, think very carefully about what the
[minimum viable change](https://about.gitlab.com/handbook/product/#the-minimally-viable-change)
is. Can you split the functionality into two smaller MRs? Can you submit only the
backend/API code? Can you start with a very simple UI? Can you do just a part of the
refactor?

Small MRs which are more easily reviewed, lead to higher code quality which is
more important to GitLab than having a minimal commit log. The smaller an MR is,
the more likely it will be merged quickly. After that you can send more MRs to
enhance and expand the feature. The [How to get faster PR reviews](https://github.com/kubernetes/kubernetes/blob/release-1.5/docs/devel/faster_reviews.md)
document from the Kubernetes team also has some great points regarding this.

### Commit messages guidelines

When writing commit messages, please follow the guidelines below:

- The commit subject must contain at least 3 words.
- The commit subject should ideally contain up to 50 characters,
  and must not be longer than 72 characters.
- The commit subject must start with a capital letter.
- The commit subject must not end with a period.
- The commit subject and body must be separated by a blank line.
- The commit body must not contain more than 72 characters per line.
- Commits that change 30 or more lines across at least 3 files must
  describe these changes in the commit body.
- The commit subject or body must not contain Emojis.
- Use issues and merge requests' full URLs instead of short references,
  as they are displayed as plain text outside of GitLab.
- The merge request must not contain more than 10 commit messages.

If the guidelines are not met, the MR will not pass the
[Danger checks](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/danger/commit_messages/Dangerfile).
For more information see [How to Write a Git Commit Message](https://chris.beams.io/posts/git-commit/).

## Contribution acceptance criteria

To make sure that your merge request can be approved, please ensure that it meets
the contribution acceptance criteria below:

1. The change is as small as possible.
1. Include proper tests and make all tests pass (unless it contains a test
   exposing a bug in existing code). Every new class should have corresponding
   unit tests, even if the class is exercised at a higher level, such as a feature test.
   - If a failing CI build seems to be unrelated to your contribution, you can try
     restarting the failing CI job, rebasing from master to bring in updates that
     may resolve the failure, or if it has not been fixed yet, ask a developer to
     help you fix the test.
1. The MR initially contains a few logically organized commits.
1. The changes can merge without problems. If not, you should rebase if you're the
   only one working on your feature branch, otherwise merge `master`.
1. Only one specific issue is fixed or one specific feature is implemented. Do not
   combine things; send separate merge requests for each issue or feature.
1. Migrations should do only one thing (e.g., create a table, move data to a new
   table, or remove an old table) to aid retrying on failure.
1. Contains functionality that other users will benefit from.
1. Doesn't add configuration options or settings options since they complicate making
   and testing future changes.
1. Changes do not degrade performance:
   - Avoid repeated polling of endpoints that require a significant amount of overhead.
   - Check for N+1 queries via the SQL log or [`QueryRecorder`](../merge_request_performance_guidelines.md).
   - Avoid repeated access of the filesystem.
   - Use [polling with ETag caching](../polling.md) if needed to support real-time features.
1. If the merge request adds any new libraries (gems, JavaScript libraries, etc.),
   they should conform to our [Licensing guidelines](../licensing.md). See those
   instructions for help if the "license-finder" test fails with a
   `Dependencies that need approval` error. Also, make the reviewer aware of the new
   library and explain why you need it.
1. The merge request meets GitLab's [definition of done](#definition-of-done), below.

## Definition of done

If you contribute to GitLab please know that changes involve more than just
code. We use the following [definition of done](https://www.agilealliance.org/glossary/definition-of-done).
Your contribution is not *done* until you have made sure it meets all of these
requirements.

1. Clear description explaining the relevancy of the contribution.
1. Working and clean code that is commented where needed.
1. [Unit, integration, and system tests](../testing_guide/index.md) that all pass
   on the CI server.
1. Performance/scalability implications have been considered, addressed, and tested.
1. [Documented](../documentation/index.md) in the `/doc` directory.
1. [Changelog entry added](../changelog.md), if necessary.
1. Reviewed by relevant (UX/FE/BE/tech writing) reviewers and all concerns are addressed.
1. Merged by a project maintainer.
1. Confirmed to be working in the [Canary stage](https://about.gitlab.com/handbook/engineering/#canary-testing) or on GitLab.com once the contribution is deployed.
1. Added to the [release post](https://about.gitlab.com/handbook/marketing/blog/release-posts/),
   if relevant.
1. Added to [the website](https://gitlab.com/gitlab-com/www-gitlab-com/blob/master/data/features.yml), if relevant.
1. [Black-box tests/end-to-end tests](../testing_guide/testing_levels.md#black-box-tests-at-the-system-level-aka-end-to-end-tests)
   added if required. Please contact [the quality team](https://about.gitlab.com/handbook/engineering/quality/#teams)
   with any questions.

## Dependencies

If you add a dependency in GitLab (such as an operating system package) please
consider updating the following, and note the applicability of each in your merge
request:

1. Note the addition in the [release blog post](https://about.gitlab.com/handbook/marketing/blog/release-posts/)
   (create one if it doesn't exist yet).
1. [The upgrade guide](../../update/upgrading_from_source.md).
1. The [GitLab Installation Guide](../../install/installation.md#1-packages-and-dependencies).
1. The [GitLab Development Kit](https://gitlab.com/gitlab-org/gitlab-development-kit).
1. The [CI environment preparation](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/scripts/prepare_build.sh).
1. The [Omnibus package creator](https://gitlab.com/gitlab-org/omnibus-gitlab).
