Merge branch 'docs/30141-improve-contributing-guide' into 'master'

Resolve "Combine all GitLab workflow documentation to CONTRIBUTING.md"

Closes #30141

See merge request !10991

Former-commit-id: 985737fd

CONTRIBUTING.md

@@ -13,27 +13,29 @@ _This notice should stay as the first item in the CONTRIBUTING.MD file._
 <!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
 **Table of Contents**  *generated with [DocToc](https://github.com/thlorenz/doctoc)*
-- [Contributor license agreement](#contributor-license-agreement)
 - [Contribute to GitLab](#contribute-to-gitlab)
 - [Security vulnerability disclosure](#security-vulnerability-disclosure)
 - [Closing policy for issues and merge requests](#closing-policy-for-issues-and-merge-requests)
 - [Helping others](#helping-others)
 - [I want to contribute!](#i-want-to-contribute)
-- [Implement design & UI elements](#implement-design-ui-elements)
-- [Release retrospective and kickoff](#release-retrospective-and-kickoff)
-    - [Retrospective](#retrospective)
-    - [Kickoff](#kickoff)
+- [Workflow labels](#workflow-labels)
+  - [Type labels (~"feature proposal", ~bug, ~customer, etc.)](#type-labels-feature-proposal-bug-customer-etc)
+  - [Subject labels (~wiki, ~"container registry", ~ldap, ~api, etc.)](#subject-labels-wiki-container-registry-ldap-api-etc)
+  - [Team labels (~CI, ~Discussion, ~Edge, ~Frontend, ~Platform, etc.)](#team-labels-ci-discussion-edge-frontend-platform-etc)
+  - [Priority labels (~Deliverable and ~Stretch)](#priority-labels-deliverable-and-stretch)
+  - [Label for community contributors (~"Accepting Merge Requests")](#label-for-community-contributors-accepting-merge-requests)
+- [Implement design & UI elements](#implement-design--ui-elements)
 - [Issue tracker](#issue-tracker)
-    - [Feature proposals](#feature-proposals)
-    - [Issue tracker guidelines](#issue-tracker-guidelines)
-    - [Issue weight](#issue-weight)
-    - [Regression issues](#regression-issues)
-    - [Technical debt](#technical-debt)
-    - [Stewardship](#stewardship)
+  - [Issue triaging](#issue-triaging)
+  - [Feature proposals](#feature-proposals)
+  - [Issue tracker guidelines](#issue-tracker-guidelines)
+  - [Issue weight](#issue-weight)
+  - [Regression issues](#regression-issues)
+  - [Technical debt](#technical-debt)
+  - [Stewardship](#stewardship)
 - [Merge requests](#merge-requests)
-    - [Merge request guidelines](#merge-request-guidelines)
-    - [Contribution acceptance criteria](#contribution-acceptance-criteria)
-- [Changes for Stable Releases](#changes-for-stable-releases)
+  - [Merge request guidelines](#merge-request-guidelines)
+  - [Contribution acceptance criteria](#contribution-acceptance-criteria)
 - [Definition of done](#definition-of-done)
 - [Style guides](#style-guides)
 - [Code of conduct](#code-of-conduct)
@@ -103,34 +105,125 @@ contributing to GitLab.
 ## Workflow labels
-Labelling issues is described in the [GitLab Inc engineering workflow].
-## Implement design & UI elements
-Please see the [UX Guide for GitLab].
-## Release retrospective and kickoff
-### Retrospective
-After each release, we have a retrospective call where we discuss what went well,
-what went wrong, and what we can improve for the next release. The
-[retrospective notes] are public and you are invited to comment on them.
-If you're interested, you can even join the
-[retrospective call][retro-kickoff-call], on the first working day after the
-22nd at 6pm CET / 9am PST.
-### Kickoff
-Before working on the next release, we have a
-kickoff call to explain what we expect to ship in the next release. The
-[kickoff notes] are public and you are invited to comment on them.
-If you're interested, you can even join the [kickoff call][retro-kickoff-call],
-on the first working day after the 7th at 6pm CET / 9am PST..
-[retrospective notes]: https://docs.google.com/document/d/1nEkM_7Dj4bT21GJy0Ut3By76FZqCfLBmFQNVThmW2TY/edit?usp=sharing
-[kickoff notes]: https://docs.google.com/document/d/1ElPkZ90A8ey_iOkTvUs_ByMlwKK6NAB2VOK5835wYK0/edit?usp=sharing
-[retro-kickoff-call]: https://gitlab.zoom.us/j/918821206
+To allow for asynchronous issue handling, we use [milestones][milestones-page]
+and [labels][labels-page]. Leads and product managers handle most of the
+scheduling into milestones. Labelling is a task for everyone.
+Most issues will have labels for at least one of the following:
+- Type: ~"feature proposal", ~bug, ~customer, etc.
+- Subject: ~wiki, ~"container registry", ~ldap, ~api, etc.
+- Team: ~CI, ~Discussion, ~Edge, ~Frontend, ~Platform, etc.
+- Priority: ~Deliverable, ~Stretch
+
+All labels, their meaning and priority are defined on the
+[labels page][labels-page].
+
+If you come across an issue that has none of these, and you're allowed to set
+labels, you can _always_ add the team and type, and often also the subject.
+
+[milestones-page]: https://gitlab.com/gitlab-org/gitlab-ce/milestones
+[labels-page]: https://gitlab.com/gitlab-org/gitlab-ce/labels
+
+### Type labels (~"feature proposal", ~bug, ~customer, etc.)
+
+Type labels are very important. They define what kind of issue this is. Every
+issue should have one or more.
+
+Examples of type labels are ~"feature proposal", ~bug, ~customer, ~security,
+and ~"direction".
+
+A number of type labels have a priority assigned to them, which automatically
+makes them float to the top, depending on their importance.
+
+Type labels are always lowercase, and can have any color, besides blue (which is
+already reserved for subject labels).
+
+The descriptions on the [labels page][labels-page] explain what falls under each type label.
+
+### Subject labels (~wiki, ~"container registry", ~ldap, ~api, etc.)
+
+Subject labels are labels that define what area or feature of GitLab this issue
+hits. They are not always necessary, but very convenient.
+
+If you are an expert in a particular area, it makes it easier to find issues to
+work on. You can also subscribe to those labels to receive an email each time an
+issue is labelled with a subject label corresponding to your expertise.
+
+Examples of subject labels are ~wiki, ~"container registry", ~ldap, ~api,
+~issues, ~"merge requests", ~labels, and ~"container registry".
+
+Subject labels are always all-lowercase.
+
+### Team labels (~CI, ~Discussion, ~Edge, ~Frontend, ~Platform, etc.)
+
+Team labels specify what team is responsible for this issue.
+Assigning a team label makes sure issues get the attention of the appropriate
+people.
+
+The current team labels are ~Build, ~CI, ~Discussion, ~Documentation, ~Edge,
+~Frontend, ~Gitaly, ~Platform, ~Prometheus, ~Release, and ~"UX".
+
+The descriptions on the [labels page][labels-page] explain what falls under the
+responsibility of each team.
+
+Team labels are always capitalized so that they show up as the first label for
+any issue.
+
+### Priority labels (~Deliverable and ~Stretch)
+Priority labels help us clearly communicate expectations of the work for the
+release. There are two levels of priority labels:
+- ~Deliverable: Issues that are expected to be delivered in the current
+  milestone.
+- ~Stretch: Issues that are a stretch goal for delivering in the current
+  milestone. If these issues are not done in the current release, they will
+  strongly be considered for the next release.
+### Label for community contributors (~"Accepting Merge Requests")
+Issues that are beneficial to our users, 'nice to haves', that we currently do
+not have the capacity for or want to give the priority to, are labeled as
+~"Accepting Merge Requests", so the community can make a contribution.
+Community contributors can submit merge requests for any issue they want, but
+the ~"Accepting Merge Requests" label has a special meaning. It points to
+changes that:
+1. We already agreed on,
+1. Are well-defined,
+1. Are likely to get accepted by a maintainer.
+
+We want to avoid a situation when a contributor picks an
+~"Accepting Merge Requests" issue and then their merge request gets closed,
+because we realize that it does not fit our vision, or we want to solve it in a
+different way.
+
+We add the ~"Accepting Merge Requests" label to:
+
+- Low priority ~bug issues (i.e. we do not add it to the bugs that we want to
+solve in the ~"Next Patch Release")
+- Small ~"feature proposal" that do not need ~UX / ~"Product work", or for which
+the ~UX / ~"Product work" is already done
+- Small ~"technical debt" issues
+
+After adding the ~"Accepting Merge Requests" label, we try to estimate the
+[weight](#issue-weight) of the issue. We use issue weight to let contributors
+know how difficult the issue is. Additionally:
+
+- We advertise [~"Accepting Merge Requests" issues with weight < 5][up-for-grabs]
+  as suitable for people that have never contributed to GitLab before on the
+  [Up For Grabs campaign](http://up-for-grabs.net)
+- We encourage people that have never contributed to any open source project to
+  look for [~"Accepting Merge Requests" issues with a weight of 1][firt-timers]
+
+[up-for-grabs]: https://gitlab.com/gitlab-org/gitlab-ce/issues?label_name=Accepting+Merge+Requests&scope=all&sort=weight_asc&state=opened
+[firt-timers]: https://gitlab.com/gitlab-org/gitlab-ce/issues?label_name%5B%5D=Accepting+Merge+Requests&scope=all&sort=upvotes_desc&state=opened&weight=1
+
+## Implement design & UI elements
+
+Please see the [UX Guide for GitLab].
 ## Issue tracker
@@ -154,6 +247,21 @@ If it happens that you know the solution to an existing bug, please first
 open the issue in order to keep track of it and then open the relevant merge
 request that potentially fixes it.
+### Issue triaging
+
+Our issue triage policies are [described in our handbook]. You are very welcome
+to help the GitLab team triage issues. We also organize [issue bash events] once
+every quarter.
+
+The most important thing is making sure valid issues receive feedback from the
+development team. Therefore the priority is mentioning developers that can help
+on those issues. Please select someone with relevant experience from the
+[GitLab team][team]. If there is nobody mentioned with that expertise look in
+the commit history for the affected files to find someone.
+
+[described in our handbook]: https://about.gitlab.com/handbook/engineering/issues/issue-triage-policies/
+[issue bash events]: https://gitlab.com/gitlab-org/gitlab-ce/issues/17815
+
 ### Feature proposals
 To create a feature proposal for CE, open an issue on the
@@ -327,13 +435,17 @@ request is as follows:
      "Description" field.
   1. If you are contributing documentation, choose `Documentation` from the
      "Choose a template" menu and fill in the template.
+  1. Mention the issue(s) your merge request solves, using the `Solves #XXX` or
+    `Closes #XXX` syntax to auto-close the issue(s) once the merge request will
+    be merged.
+1. If you're allowed to, set a relevant milestone and labels
 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,
    `grep css-class ./app -R`
-1. Link any relevant [issues][ce-tracker] in the merge request description and
-   leave a comment on them with a link back to the MR
 1. Be prepared to answer questions and incorporate feedback even if requests
    for this arrive weeks or months after your MR submission
+  1. If a discussion has been addressed, select the "Resolve discussion" button
+    beneath it to mark it resolved.
 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](doc/development/shell_commands.md)
@@ -369,24 +481,6 @@ Please ensure that your merge request meets the contribution acceptance criteria
 When having your code reviewed and when reviewing merge requests please take the
 [code review guidelines](doc/development/code_review.md) into account.
-### Getting your merge request reviewed, approved, and merged
-
-There are a few rules to get your merge request accepted:
-
-1. Your merge request should only be **merged by a [maintainer][team]**.
-  1. If your merge request includes only backend changes [^1], it must be
-    **approved by a [backend maintainer][team]**.
-  1. If your merge request includes only frontend changes [^1], it must be
-    **approved by a [frontend maintainer][team]**.
-  1. If your merge request includes frontend and backend changes [^1], it must
-    be **approved by a [frontend and a backend maintainer][team]**.
-1. To lower the amount of merge requests maintainers need to review, you can
-  ask or assign any [reviewers][team] for a first review.
-  1. If you need some guidance (e.g. it's your first merge request), feel free
-    to ask one of the [Merge request coaches][team].
-  1. The reviewer will assign the merge request to a maintainer once the
-    reviewer is satisfied with the state of the merge request.
-
 ### Contribution acceptance criteria
 1. The change is as small as possible
@@ -416,8 +510,7 @@ There are a few rules to get your merge request accepted:
 1. If you need polling to support real-time features, please use
    [polling with ETag caching][polling-etag].
 1. Changes after submitting the merge request should be in separate commits
-   (no squashing). If necessary, you will be asked to squash when the review is
-   over, before merging.
+   (no squashing).
 1. It conforms to the [style guides](#style-guides) and the following:
     - If your change touches a line that does not follow the style, modify the
       entire line to follow it. This prevents linting tools from generating warnings.
@@ -428,19 +521,6 @@ There are a few rules to get your merge request accepted:
    See the instructions in that document for help if your MR fails the
    "license-finder" test with a "Dependencies that need approval" error.
-## Changes for Stable Releases
-
-Sometimes certain changes have to be added to an existing stable release.
-Two examples are bug fixes and performance improvements. In these cases the
-corresponding merge request should be updated to have the following:
-
-1. A milestone indicating what release the merge request should be merged into.
-1. The label "Pick into Stable"
-
-This makes it easier for release managers to keep track of what still has to be
-merged and where changes have to be merged into.
-Like all merge requests the target should be master so all bugfixes are in master.
-
 ## Definition of done
 If you contribute to GitLab please know that changes involve more than just
@@ -449,16 +529,16 @@ the feature you contribute through all of these steps.
 1. Description explaining the relevancy (see following item)
 1. Working and clean code that is commented where needed
-1. Unit and integration tests that pass on the CI server
+1. [Unit and system tests][testing] that pass on the CI server
 1. Performance/scalability implications have been considered, addressed, and tested
-1. [Documented][doc-styleguide] in the /doc directory
-1. Changelog entry added
+1. [Documented][doc-styleguide] in the `/doc` directory
+1. [Changelog entry added][changelog], if necessary
 1. Reviewed and any concerns are addressed
-1. Merged by the project lead
-1. Added to the release blog article
-1. Added to [the website](https://gitlab.com/gitlab-com/www-gitlab-com/) if relevant
+1. Merged by a project maintainer
+1. Added to the release blog article, if relevant
+1. Added to [the website](https://gitlab.com/gitlab-com/www-gitlab-com/), if relevant
 1. Community questions answered
-1. Answers to questions radiated (in docs/wiki/etc.)
+1. Answers to questions radiated (in docs/wiki/support etc.)
 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
@@ -481,7 +561,7 @@ merge request:
     - string literal quoting style **Option A**: single quoted by default
 1.  [Rails](https://github.com/bbatsov/rails-style-guide)
 1.  [Newlines styleguide][newlines-styleguide]
-1.  [Testing](doc/development/testing.md)
+1.  [Testing][testing]
 1.  [JavaScript styleguide][js-styleguide]
 1.  [SCSS styleguide][scss-styleguide]
 1.  [Shell commands](doc/development/shell_commands.md) created by GitLab
@@ -558,6 +638,7 @@ available at [http://contributor-covenant.org/version/1/1/0/](http://contributor
 [license-finder-doc]: doc/development/licensing.md
 [GitLab Inc engineering workflow]: https://about.gitlab.com/handbook/engineering/workflow/#labelling-issues
 [polling-etag]: https://docs.gitlab.com/ce/development/polling.html
+[testing]: doc/development/testing.md
 [^1]: Please note that specs other than JavaScript specs are considered backend
       code.

PROCESS.md

-# GitLab Contributing Process
+## GitLab Core Team & GitLab Inc. Contribution Process
+
+---
+
+<!-- START doctoc generated TOC please keep comment here to allow auto update -->
+<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
+**Table of Contents**  *generated with [DocToc](https://github.com/thlorenz/doctoc)*
+
+- [Purpose of describing the contributing process](#purpose-of-describing-the-contributing-process)
+- [Common actions](#common-actions)
+  - [Merge request coaching](#merge-request-coaching)
+- [Assigning issues](#assigning-issues)
+- [Be kind](#be-kind)
+- [Feature freeze on the 7th for the release on the 22nd](#feature-freeze-on-the-7th-for-the-release-on-the-22nd)
+  - [Between the 1st and the 7th](#between-the-1st-and-the-7th)
+  - [On the 7th](#on-the-7th)
+  - [After the 7th](#after-the-7th)
+- [Release retrospective and kickoff](#release-retrospective-and-kickoff)
+  - [Retrospective](#retrospective)
+  - [Kickoff](#kickoff)
+- [Copy & paste responses](#copy--paste-responses)
+  - [Improperly formatted issue](#improperly-formatted-issue)
+  - [Issue report for old version](#issue-report-for-old-version)
+  - [Support requests and configuration questions](#support-requests-and-configuration-questions)
+  - [Code format](#code-format)
+  - [Issue fixed in newer version](#issue-fixed-in-newer-version)
+  - [Improperly formatted merge request](#improperly-formatted-merge-request)
+  - [Inactivity close of an issue](#inactivity-close-of-an-issue)
+  - [Inactivity close of a merge request](#inactivity-close-of-a-merge-request)
+  - [Accepting merge requests](#accepting-merge-requests)
+  - [Only accepting merge requests with green tests](#only-accepting-merge-requests-with-green-tests)
+  - [Closing down the issue tracker on GitHub](#closing-down-the-issue-tracker-on-github)
+
+<!-- END doctoc generated TOC please keep comment here to allow auto update -->
+
+---
 ## Purpose of describing the contributing process
-Below we describe the contributing process to GitLab for two reasons. So that
-contributors know what to expect from maintainers (possible responses, friendly
-treatment, etc.). And so that maintainers know what to expect from contributors
-(use the latest version, ensure that the issue is addressed, friendly treatment,
-etc.).
+Below we describe the contributing process to GitLab for two reasons:
+
+1. Contributors know what to expect from maintainers (possible responses, friendly
+  treatment, etc.)
+1. Maintainers know what to expect from contributors (use the latest version,
+  ensure that the issue is addressed, friendly treatment, etc.).
 - [GitLab Inc engineers should refer to the engineering workflow document](https://about.gitlab.com/handbook/engineering/workflow/)
 ## Common actions
-### Issue triaging
-
-Our issue triage policies are [described in our handbook]. You are very welcome
-to help the GitLab team triage issues. We also organize [issue bash events] once
-every quarter.
-
-The most important thing is making sure valid issues receive feedback from the
-development team. Therefore the priority is mentioning developers that can help
-on those issues. Please select someone with relevant experience from
-[GitLab team][team]. If there is nobody mentioned with that expertise
-look in the commit history for the affected files to find someone. Avoid
-mentioning the lead developer, this is the person that is least likely to give a
-timely response. If the involvement of the lead developer is needed the other
-core team members will mention this person.
-
-[described in our handbook]: https://about.gitlab.com/handbook/engineering/issues/issue-triage-policies/
-[issue bash events]: https://gitlab.com/gitlab-org/gitlab-ce/issues/17815
-
 ### Merge request coaching
 Several people from the [GitLab team][team] are helping community members to get
@@ -37,12 +55,6 @@ their contributions accepted by meeting our [Definition of done][done].
 What you can expect from them is described at https://about.gitlab.com/jobs/merge-request-coach/.
-## Workflow labels
-
-Labelling issues is described in the [GitLab Inc engineering workflow].
-
-[GitLab Inc engineering workflow]: https://about.gitlab.com/handbook/engineering/workflow/#labelling-issues
-
 ## Assigning issues
 If an issue is complex and needs the attention of a specific person, assignment is a good option but assigning issues might discourage other people from contributing to that issue. We need all the contributions we can get so this should never be discouraged. Also, an assigned person might not have time for a few weeks, so others should feel free to takeover.
@@ -146,6 +158,29 @@ release should have the correct milestone assigned _and_ have the label
 Merge requests without a milestone and this label will
 not be merged into any stable branches.
+## Release retrospective and kickoff
+
+### Retrospective
+
+After each release, we have a retrospective call where we discuss what went well,
+what went wrong, and what we can improve for the next release. The
+[retrospective notes] are public and you are invited to comment on them.
+If you're interested, you can even join the
+[retrospective call][retro-kickoff-call], on the first working day after the
+22nd at 6pm CET / 9am PST.
+
+### Kickoff
+
+Before working on the next release, we have a
+kickoff call to explain what we expect to ship in the next release. The
+[kickoff notes] are public and you are invited to comment on them.
+If you're interested, you can even join the [kickoff call][retro-kickoff-call],
+on the first working day after the 7th at 6pm CET / 9am PST..
+
+[retrospective notes]: https://docs.google.com/document/d/1nEkM_7Dj4bT21GJy0Ut3By76FZqCfLBmFQNVThmW2TY/edit?usp=sharing
+[kickoff notes]: https://docs.google.com/document/d/1ElPkZ90A8ey_iOkTvUs_ByMlwKK6NAB2VOK5835wYK0/edit?usp=sharing
+[retro-kickoff-call]: https://gitlab.zoom.us/j/918821206
+
 ## Copy & paste responses
 ### Improperly formatted issue

doc/development/code_review.md

 # Code Review Guidelines
+## Getting your merge request reviewed, approved, and merged
+
+There are a few rules to get your merge request accepted:
+
+1. Your merge request should only be **merged by a [maintainer][team]**.
+  1. If your merge request includes only backend changes [^1], it must be
+    **approved by a [backend maintainer][team]**.
+  1. If your merge request includes only frontend changes [^1], it must be
+    **approved by a [frontend maintainer][team]**.
+  1. If your merge request includes frontend and backend changes [^1], it must
+    be **approved by a [frontend and a backend maintainer][team]**.
+1. To lower the amount of merge requests maintainers need to review, you can
+  ask or assign any [reviewers][team] for a first review.
+  1. If you need some guidance (e.g. it's your first merge request), feel free
+    to ask one of the [Merge request coaches][team].
+  1. The reviewer will assign the merge request to a maintainer once the
+    reviewer is satisfied with the state of the merge request.
+
+## Best practices
+
 This guide contains advice and best practices for performing code review, and
 having your code reviewed.
@@ -12,7 +32,7 @@ of colleagues and contributors. However, the final decision to accept a merge
 request is up to one the project's maintainers, denoted on the
 [team page](https://about.gitlab.com/team).
-## Everyone
+### Everyone
 - Accept that many programming decisions are opinions. Discuss tradeoffs, which
   you prefer, and reach a resolution quickly.
@@ -31,8 +51,11 @@ request is up to one the project's maintainers, denoted on the
 - Consider one-on-one chats or video calls if there are too many "I didn't
   understand" or "Alternative solution:" comments. Post a follow-up comment
   summarizing one-on-one discussion.
-## Having your code reviewed
+- If you ask a question to a specific person, always start the comment by
+  mentioning them; this will ensure they see it if their notification level is
+  set to "mentioned" and other people will understand they don't have to respond.
+### Having your code reviewed
 Please keep in mind that code review is a process that can take multiple
 iterations, and reviewers may spot things later that they may not have seen the
@@ -50,11 +73,12 @@ first time.
 - Extract unrelated changes and refactorings into future merge requests/issues.
 - Seek to understand the reviewer's perspective.
 - Try to respond to every comment.
+- Let the reviewer select the "Resolve discussion" buttons.
 - Push commits based on earlier rounds of feedback as isolated commits to the
   branch. Do not squash until the branch is ready to merge. Reviewers should be
   able to read individual updates based on their earlier feedback.
-## Reviewing code
+### Reviewing code
 Understand why the change is necessary (fixes a bug, improves the user
 experience, refactors the existing code). Then:
@@ -69,12 +93,19 @@ experience, refactors the existing code). Then:
   someone else would be confused by it as well.
 - After a round of line notes, it can be helpful to post a summary note such as
   "LGTM :thumbsup:", or "Just a couple things to address."
+- Assign the merge request to the author if changes are required following your
+  review.
+- Set the milestone before merging a merge request.
 - Avoid accepting a merge request before the job succeeds. Of course, "Merge
   When Pipeline Succeeds" (MWPS) is fine.
 - If you set the MR to "Merge When Pipeline Succeeds", you should take over
   subsequent revisions for anything that would be spotted after that.
-## The right balance
+- Consider using the [Squash and
+  merge][squash-and-merge] feature when the merge request has a lot of commits.
+
+[squash-and-merge]: https://docs.gitlab.com/ee/user/project/merge_requests/squash_and_merge.html#squash-and-merge
+### The right balance
 One of the most difficult things during code review is finding the right
 balance in how deep the reviewer can interfere with the code created by a
@@ -100,7 +131,7 @@ reviewee.
   tomorrow. When you are not able to find the right balance, ask other people
   about their opinion.
-## Credits
+### Credits
 Largely based on the [thoughtbot code review guide].