Improve the contributing documentation

This removes duplicated content from CONTRIBUTING.md and consolidate
everything under doc/development/contributing/.

This also fixes missing links.

Lastly, this moves the style guides from the "Implement design & UI
elements" page to a new "Style guides" page.

Signed-off-by: Rémy Coutable <remy@rymai.me>

7 files changed, 181 insertions, 146 deletions

diff --git a/doc/development/README.md b/doc/development/README.md
index 43d3865da0e..0491e8d489f 100644
--- a/doc/development/README.md
+++ b/doc/development/README.md
@@ -8,7 +8,7 @@ description: 'Learn how to contribute to GitLab.'
 ## Get started!
 
 - Set up GitLab's development environment with [GitLab Development Kit (GDK)](https://gitlab.com/gitlab-org/gitlab-development-kit/blob/master/doc/howto/README.md)
-- [GitLab contributing guide](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md)
+- [GitLab contributing guide](contributing/index.md)
 - [Architecture](architecture.md) of GitLab
 - [Rake tasks](rake_tasks.md) for development
 
diff --git a/doc/development/contributing/community_roles.md b/doc/development/contributing/community_roles.md
index c508969f7f4..b9c369286d2 100644
--- a/doc/development/contributing/community_roles.md
+++ b/doc/development/contributing/community_roles.md
@@ -9,4 +9,8 @@ GitLab community members and their privileges/responsibilities.
 | Developer |Has access to GitLab internal infrastructure & issues (e.g. HR-related) | GitLab employee or a Core Team member (with an NDA) |
 | Contributor | Can make contributions to all GitLab public projects | Have a GitLab.com account |
 
-[List of current reviewers/maintainers](https://about.gitlab.com/handbook/engineering/projects/#gitlab-ce) 
\ No newline at end of file
+[List of current reviewers/maintainers](https://about.gitlab.com/handbook/engineering/projects/#gitlab-ce).
+
+---
+
+[Return to Contributing documentation](index.md)
diff --git a/doc/development/contributing/design.md b/doc/development/contributing/design.md
index be7891061f9..79750878aac 100644
--- a/doc/development/contributing/design.md
+++ b/doc/development/contributing/design.md
@@ -13,7 +13,10 @@ There is a special type label called ~"product discovery". It represents a disco
 
 ~"product discovery" issues are like any other issue and should contain a milestone label, ~"Deliverable" or ~"Stretch", when scheduled in the current milestone.
 
-The initial issue should be about the problem we are solving. If a separate [product discovery issue](#product-discovery-issues) is needed for additional research and design work, it will be created by a PM or UX person. Assign the ~UX, ~"product discovery" and ~"Deliverable" labels, add a milestone and use a title that makes it clear that the scheduled issue is product discovery
+The initial issue should be about the problem we are solving. If a separate [product discovery issue](https://about.gitlab.com/handbook/engineering/ux/ux-department-workflow/#how-we-use-labels)
+is needed for additional research and design work, it will be created by a PM or UX person.
+Assign the ~UX, ~"product discovery" and ~"Deliverable" labels, add a milestone and
+use a title that makes it clear that the scheduled issue is product discovery
 (e.g. `Product discovery for XYZ`).
 
 In order to complete a product discovery issue in a release, you must complete the following:
@@ -23,34 +26,6 @@ In order to complete a product discovery issue in a release, you must complete t
 1. Copy the design to the description of the delivery issue for which the product discovery issue was created. Do not simply refer to the product discovery issue as a separate source of truth.
 1. In some cases, a product discovery issue also identifies future enhancements that will not go into the issue that originated the product discovery issue. For these items, create new issues containing the designs to ensure they are not lost. Put the issues in the backlog if they are agreed upon as good ideas. Otherwise leave them for triage.
 
-## Style guides
-
-1. [Ruby](https://github.com/bbatsov/ruby-style-guide).
-   Important sections include [Source Code Layout][rss-source] and
-   [Naming][rss-naming]. Use:
-   - multi-line method chaining style **Option A**: dot `.` on the second line
-   - 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][testing]
-1. [JavaScript styleguide][js-styleguide]
-1. [SCSS styleguide][scss-styleguide]
-1. [Shell commands](../shell_commands.md) created by GitLab
-   contributors to enhance security
-1. [Database Migrations](../migration_style_guide.md)
-1. [Markdown](http://www.cirosantilli.com/markdown-styleguide)
-1. [Documentation styleguide](https://docs.gitlab.com/ee/development/documentation/styleguide.html)
-1. Interface text should be written subjectively instead of objectively. It
-   should be the GitLab core team addressing a person. It should be written in
-   present time and never use past tense (has been/was). For example instead
-   of _prohibited this user from being saved due to the following errors:_ the
-   text should be _sorry, we could not create your account because:_
-1. Code should be written in [US English][us-english]
-
-This is also the style used by linting tools such as
-[RuboCop](https://github.com/bbatsov/rubocop),
-[PullReview](https://www.pullreview.com/) and [Hound CI](https://houndci.com).
-
 ---
 
 [Return to Contributing documentation](index.md)
diff --git a/doc/development/contributing/index.md b/doc/development/contributing/index.md
index f4486ae3549..29af8dcb9bb 100644
--- a/doc/development/contributing/index.md
+++ b/doc/development/contributing/index.md
@@ -1,22 +1,24 @@
 # Contribute to GitLab
 
-For a first-time step-by-step guide to the contribution process, see
-["Contributing to GitLab"](https://about.gitlab.com/contributing/).
-
 Thank you for your interest in contributing to GitLab. This guide details how
-to contribute to GitLab in a way that is efficient for everyone.
+to contribute to GitLab in a way that is easy for everyone.
+
+For a first-time step-by-step guide to the contribution process, please see
+["Contributing to GitLab"](https://about.gitlab.com/contributing/).
 
-Looking for something to work on? Look for issues with the label [Accepting Merge Requests](#i-want-to-contribute).
+Looking for something to work on? Look for issues in the [Backlog (Accepting merge requests) milestone](#i-want-to-contribute).
 
-GitLab comes into two flavors, GitLab Community Edition (CE) our free and open
+GitLab comes in two flavors, GitLab Community Edition (CE) our free and open
 source edition, and GitLab Enterprise Edition (EE) which is our commercial
 edition. Throughout this guide you will see references to CE and EE for
 abbreviation.
 
-If you have read this guide and want to know how the GitLab [core team]
+To get an overview of GitLab community membership including those that would be reviewing or merging your contributions, please visit [the community roles page](community_roles.md).
+
+If you want to know how the GitLab [core team]
 operates please see [the GitLab contributing process](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/PROCESS.md).
 
-- [GitLab Inc engineers should refer to the engineering workflow document](https://about.gitlab.com/handbook/engineering/workflow/)
+[GitLab Inc engineers should refer to the engineering workflow document](https://about.gitlab.com/handbook/engineering/workflow/)
 
 ## Security vulnerability disclosure
 
@@ -28,33 +30,77 @@ vulnerabilities.
 
 ## Code of conduct
 
-As contributors and maintainers of this project, we pledge to respect all
-people who contribute through reporting issues, posting feature requests,
-updating documentation, submitting pull requests or patches, and other
-activities.
+### Our Pledge
+
+In the interest of fostering an open and welcoming environment, we as
+contributors and maintainers pledge to making participation in our project and
+our community a harassment-free experience for everyone, regardless of age, body
+size, disability, ethnicity, sex characteristics, gender identity and expression,
+level of experience, education, socio-economic status, nationality, personal
+appearance, race, religion, or sexual identity and orientation.
+
+### Our Standards
 
-We are committed to making participation in this project a harassment-free
-experience for everyone, regardless of level of experience, gender, gender
-identity and expression, sexual orientation, disability, personal appearance,
-body size, race, ethnicity, age, or religion.
+Examples of behavior that contributes to creating a positive environment
+include:
 
-Examples of unacceptable behavior by participants include the use of sexual
-language or imagery, derogatory comments or personal attacks, trolling, public
-or private harassment, insults, or other unprofessional conduct.
+* Using welcoming and inclusive language
+* Being respectful of differing viewpoints and experiences
+* Gracefully accepting constructive criticism
+* Focusing on what is best for the community
+* Showing empathy towards other community members
+
+Examples of unacceptable behavior by participants include:
+
+* The use of sexualized language or imagery and unwelcome sexual attention or
+  advances
+* Trolling, insulting/derogatory comments, and personal or political attacks
+* Public or private harassment
+* Publishing others' private information, such as a physical or electronic
+  address, without explicit permission
+* Other conduct which could reasonably be considered inappropriate in a
+  professional setting
+
+### Our Responsibilities
+
+Project maintainers are responsible for clarifying the standards of acceptable
+behavior and are expected to take appropriate and fair corrective action in
+response to any instances of unacceptable behavior.
 
 Project maintainers have the right and responsibility to remove, edit, or
 reject comments, commits, code, wiki edits, issues, and other contributions
-that are not aligned to this Code of Conduct. Project maintainers who do not
-follow the Code of Conduct may be removed from the project team.
+that are not aligned to this Code of Conduct, or to ban temporarily or
+permanently any contributor for other behaviors that they deem inappropriate,
+threatening, offensive, or harmful.
+
+### Scope
+
+This Code of Conduct applies both within project spaces and in public spaces
+when an individual is representing the project or its community. Examples of
+representing a project or community include using an official project e-mail
+address, posting via an official social media account, or acting as an appointed
+representative at an online or offline event. Representation of a project may be
+further defined and clarified by project maintainers.
+
+### Enforcement
 
-This code of conduct applies both within project spaces and in public spaces
-when an individual is representing the project or its community.
+Instances of abusive, harassing, or otherwise unacceptable behavior may be
+reported by contacting the project team at conduct@gitlab.com. All
+complaints will be reviewed and investigated and will result in a response that
+is deemed necessary and appropriate to the circumstances. The project team is
+obligated to maintain confidentiality with regard to the reporter of an incident.
+Further details of specific enforcement policies may be posted separately.
 
-Instances of abusive, harassing, or otherwise unacceptable behavior can be
-reported by emailing `contact@gitlab.com`.
+Project maintainers who do not follow or enforce the Code of Conduct in good
+faith may face temporary or permanent repercussions as determined by other
+members of the project's leadership.
 
-This Code of Conduct is adapted from the [Contributor Covenant][contributor-covenant], version 1.1.0,
-available at [http://contributor-covenant.org/version/1/1/0/](http://contributor-covenant.org/version/1/1/0/).
+### Attribution
+
+This Code of Conduct is adapted from the [Contributor Covenant][homepage], version 1.4,
+available at https://www.contributor-covenant.org/version/1/4/code-of-conduct.html
+
+[homepage]: https://www.contributor-covenant.org
 
 ## Closing policy for issues and merge requests
 
@@ -87,8 +133,8 @@ the remaining issues on the GitHub issue tracker.
 
 ## I want to contribute!
 
-If you want to contribute to GitLab [issues with the label `Accepting Merge Requests` and small weight][accepting-mrs-weight]
-is a great place to start. Issues with a lower weight (1 or 2) are deemed
+If you want to contribute to GitLab, [issues in the `Backlog (Accepting merge requests)` milestone][accepting-mrs-weight]
+are a great place to start. Issues with a lower weight (1 or 2) are deemed
 suitable for beginners. These issues will be of reasonable size and challenge,
 for anyone to start contributing to GitLab. If you have any questions or need help visit [Getting Help](https://about.gitlab.com/getting-help/#discussion) to
 learn how to communicate with GitLab. If you're looking for a Gitter or Slack channel
@@ -117,93 +163,39 @@ When your code contains more than 500 changes, any major breaking changes, or an
 
 This [documentation](issue_workflow.md) outlines the current workflow labels.
 
-### Type labels
-
-This [documentation](issue_workflow.md) outlines the current type labels.
-
-### Subject labels
-
-This [documentation](issue_workflow.md) outlines the current subject labels.
-
-### Team labels
-
-This [documentation](issue_workflow.md) outlines the current team labels.
-
-### Milestone labels
-
-This [documentation](issue_workflow.md) outlines the current milestone labels.
-
-### Bug Priority labels
-
-This [documentation](issue_workflow.md) outlines the current bug priority  labels.
-
-### Bug Severity labels
-
-This [documentation](issue_workflow.md) outlines the current severity labels.
-
-#### Severity impact guidance
-
-This [documentation](issue_workflow.md) outlines the current severity impact guidance.
-
-### Label for community contributors
-
-This [documentation](issue_workflow.md) outlines the current policy regarding community contributor issues.
-
-## Implement design & UI elements
-
-This [documentation](design.md) outlines the current design and UI guidelines.
-
-## Issue tracker
-
-This [documentation](issue_workflow.md) outlines the issue tracker process.
-
-### Issue triaging
-
-This [documentation](issue_workflow.md) outlines the current issue triaging process.
-
-### Feature proposals
-
-This [documentation](issue_workflow.md) outlines the feature proposal process.
-
-### Issue tracker guidelines
-
-This [documentation](issue_workflow.md) outlines the issue tracker guidelines.
-
-### Issue weight
-
-This [documentation](issue_workflow.md) outlines the issue weight guidelines.
-
-### Regression issues
-
-This [documentation](issue_workflow.md) outlines the regression issue process.
-
-### Technical and UX debt
-
-This [documentation](issue_workflow.md) about technical and UX debt has been moved.
-
-### Stewardship
-
-This [documentation](issue_workflow.md) outlines the stewardship process.
+* [Type labels](issue_workflow.md#type-labels)
+* [Subject labels](issue_workflow.md#subject-labels)
+* [Team labels](issue_workflow.md#team-labels)
+* [Release Scoping labels](issue_workflow.md#release-scoping-labels)
+* [Priority labels](issue_workflow.md#priority-labels)
+* [Severity labels](issue_workflow.md#severity-labels)
+* [Label for community contributors](issue_workflow.md#label-for-community-contributors)
+* [Issue triaging](issue_workflow.md#issue-triaging)
+* [Feature proposals](issue_workflow.md#feature-proposals)
+* [Issue tracker guidelines](issue_workflow.md#issue-tracker-guidelines)
+* [Issue weight](issue_workflow.md#issue-weight)
+* [Regression issues](issue_workflow.md#regression-issues)
+* [Technical and UX debt](issue_workflow.md#technical-and-ux-debt)
+* [Stewardship](issue_workflow.md#stewardship)
 
 ## Merge requests
 
 This [documentation](merge_request_workflow.md) outlines the current merge request process.
 
-### Merge request guidelines
-
-This [documentation](merge_request_workflow.md) outlines the current merge request guidelines.
-
-### Contribution acceptance criteria
-
-This [documentation](merge_request_workflow.md) outlines the current acceptance criteria for contributions.
-
-## Definition of done
-
-This [documentation](merge_request_workflow.md) outlines the definition of done.
+* [Merge request guidelines](merge_request_workflow.md#merge-request-guidelines)
+* [Contribution acceptance criteria](merge_request_workflow.md#contribution-acceptance-criteria)
+* [Definition of done](merge_request_workflow.md#definition-of-done)
 
 ## Style guides
-This [documentation](design.md) outlines the current style guidelines.
+
+This [documentation](style_guides.md) outlines the current style guidelines.
 
 ---
 
 [Return to Development documentation](../README.md)
+
+[core team]: https://about.gitlab.com/core-team/
+[team]: https://about.gitlab.com/team/
+[getting-help]: https://about.gitlab.com/getting-help/
+[codetriage]: http://www.codetriage.com/gitlabhq/gitlabhq
+[accepting-mrs-weight]: https://gitlab.com/gitlab-org/gitlab-ce/issues?scope=all&utf8=✓&state=opened&assignee_id=0&milestone_title=Backlog%20(Accepting%20merge%20requests)
diff --git a/doc/development/contributing/issue_workflow.md b/doc/development/contributing/issue_workflow.md
index 1b25a5a2fb7..c0a635db12f 100644
--- a/doc/development/contributing/issue_workflow.md
+++ b/doc/development/contributing/issue_workflow.md
@@ -20,7 +20,6 @@ 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
 
@@ -208,6 +207,7 @@ project.
 [GitLab Triage]: https://gitlab.com/gitlab-org/gitlab-triage
 [scheduled pipeline]: https://gitlab.com/gitlab-org/quality/triage-ops/pipeline_schedules/10512/edit
 [quality/triage-ops]: https://gitlab.com/gitlab-org/quality/triage-ops
+[team]: https://about.gitlab.com/team/
 
 ## Feature proposals
 
@@ -235,6 +235,8 @@ need to ask one of the [core team] members to add the label, if you do not have
 If you want to create something yourself, consider opening an issue first to
 discuss whether it is interesting to include this in GitLab.
 
+[fpl]: https://gitlab.com/gitlab-org/gitlab-ce/issues?label_name=feature+proposal
+
 ## Issue tracker guidelines
 
 **[Search the issue tracker][ce-tracker]** for similar entries before
@@ -331,3 +333,7 @@ A recent example of this was the issue for
 ---
 
 [Return to Contributing documentation](index.md)
+
+[labels-page]: https://gitlab.com/gitlab-org/gitlab-ce/labels
+[ce-tracker]: https://gitlab.com/gitlab-org/gitlab-ce/issues
+[ee-tracker]: https://gitlab.com/gitlab-org/gitlab-ee/issues
diff --git a/doc/development/contributing/merge_request_workflow.md b/doc/development/contributing/merge_request_workflow.md
index 0d20e1a02dd..cc7d8a1e1db 100644
--- a/doc/development/contributing/merge_request_workflow.md
+++ b/doc/development/contributing/merge_request_workflow.md
@@ -2,9 +2,9 @@
 
 We welcome merge requests with fixes and improvements to GitLab code, tests,
 and/or documentation. The issues that are specifically suitable for
-community contributions are listed with the label
-[`Accepting Merge Requests` on our issue tracker for CE][accepting-mrs-ce]
-and [EE][accepting-mrs-ee], but you are free to contribute to any other issue
+community contributions are listed with the
+[`Backlog (Accepting merge requests)` milestone in the CE issue tracker][accepting-mrs-ce]
+and [EE issue tracker][accepting-mrs-ee], but you are free to contribute to any other issue
 you want.
 
 Please note that if an issue is marked for the current milestone either before
@@ -19,11 +19,16 @@ wireframes if the feature will also change the UI.
 Merge requests should be opened at [GitLab.com][gitlab-mr-tracker].
 
 If you are new to GitLab development (or web development in general), see the
-[I want to contribute!](#i-want-to-contribute) section to get you started with
+[I want to contribute!](index.md#i-want-to-contribute) section to get you started with
 some potentially easy issues.
 
 To start with GitLab development download the [GitLab Development Kit][gdk] and
-see the [Development section](../README.md) for some guidelines.
+see the [Development section](../../README.md) for some guidelines.
+
+[accepting-mrs-ce]: https://gitlab.com/gitlab-org/gitlab-ce/issues?milestone_title=Backlog%20(Accepting%20merge%20requests)
+[accepting-mrs-ee]: https://gitlab.com/gitlab-org/gitlab-ee/issues?milestone_title=Backlog%20(Accepting%20merge%20requests)
+[gitlab-mr-tracker]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests
+[gdk]: https://gitlab.com/gitlab-org/gitlab-development-kit
 
 ## Merge request guidelines
 
@@ -103,6 +108,10 @@ 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](../code_review.md) into account.
 
+[git-squash]: https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits
+[closed-merge-requests]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests?assignee_id=&label_name=&milestone_id=&scope=&sort=&state=closed
+[team]: https://about.gitlab.com/team/
+
 ## Contribution acceptance criteria
 
 1. The change is as small as possible
@@ -133,7 +142,7 @@ When having your code reviewed and when reviewing merge requests please take the
    [polling with ETag caching][polling-etag].
 1. Changes after submitting the merge request should be in separate commits
    (no squashing).
-1. It conforms to the [style guides](#style-guides) and the following:
+1. It conforms to the [style guides](style_guides.md) 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.
     - Don't touch neighbouring lines. As an exception, automatic mass
@@ -144,6 +153,9 @@ When having your code reviewed and when reviewing merge requests please take the
    "license-finder" test with a "Dependencies that need approval" error.
 1. The merge request meets the [definition of done](#definition-of-done).
 
+[license-finder-doc]: ../licensing.md
+[polling-etag]: ../polling.md
+
 ## Definition of done
 
 If you contribute to GitLab please know that changes involve more than just
@@ -175,6 +187,12 @@ merge request:
 1. Test suite https://gitlab.com/gitlab-org/gitlab-ce/blob/master/scripts/prepare_build.sh
 1. Omnibus package creator https://gitlab.com/gitlab-org/omnibus-gitlab
 
+[definition-of-done]: http://guide.agilealliance.org/guide/definition-of-done.html
+[testing]: ../testing_guide/index.md
+
 ---
 
 [Return to Contributing documentation](index.md)
+
+[changelog]: ../changelog.md "Generate a changelog entry"
+[doc-guidelines]: ../documentation/index.md "Documentation guidelines"
diff --git a/doc/development/contributing/style_guides.md b/doc/development/contributing/style_guides.md
new file mode 100644
index 00000000000..fb0454db7d2
--- /dev/null
+++ b/doc/development/contributing/style_guides.md
@@ -0,0 +1,40 @@
+# Style guides
+
+1. [Ruby](https://github.com/bbatsov/ruby-style-guide).
+   Important sections include [Source Code Layout][rss-source] and
+   [Naming][rss-naming]. Use:
+   - multi-line method chaining style **Option A**: dot `.` on the second line
+   - 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][testing]
+1. [JavaScript styleguide][js-styleguide]
+1. [SCSS styleguide][scss-styleguide]
+1. [Shell commands](../shell_commands.md) created by GitLab
+   contributors to enhance security
+1. [Database Migrations](../migration_style_guide.md)
+1. [Markdown](http://www.cirosantilli.com/markdown-styleguide)
+1. [Documentation styleguide](../documentation/styleguide.md)
+1. Interface text should be written subjectively instead of objectively. It
+   should be the GitLab core team addressing a person. It should be written in
+   present time and never use past tense (has been/was). For example instead
+   of _prohibited this user from being saved due to the following errors:_ the
+   text should be _sorry, we could not create your account because:_
+1. Code should be written in [US English][us-english]
+
+This is also the style used by linting tools such as
+[RuboCop](https://github.com/bbatsov/rubocop),
+[PullReview](https://www.pullreview.com/) and [Hound CI](https://houndci.com).
+
+---
+
+[Return to Contributing documentation](index.md)
+
+[rss-source]: https://github.com/bbatsov/ruby-style-guide/blob/master/README.md#source-code-layout
+[rss-naming]: https://github.com/bbatsov/ruby-style-guide/blob/master/README.md#naming
+[doc-guidelines]: ../documentation/index.md "Documentation guidelines"
+[js-styleguide]: ../fe_guide/style_guide_js.md "JavaScript styleguide"
+[scss-styleguide]: ../fe_guide/style_guide_scss.md "SCSS styleguide"
+[newlines-styleguide]: ../newlines_styleguide.md "Newlines styleguide"
+[testing]: ../testing_guide/index.md
+[us-english]: https://en.wikipedia.org/wiki/American_English