Fix "Wiki" link not appearing in navigation for projects with external wiki

## Are there points in the code the reviewer needs to double check?

No

## What are the relevant issue numbers?

Closes #21446

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [x] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !6057

Do not enforce using a hash with hidden ci key

## What does this MR do?

This MR remove the validation rule that was to strict.

## Why was this MR needed?

Enforcing hidden CI job configuration to be a hash, narrows options of using YAML anchors, and was not backwards compatbile.

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- Tests
  - [x] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Closes #21512

See merge request !6079

Remove vendor prefixes for linear-gradient CSS

## What does this MR do?
Removes the vendor prefixes for linear-gradient and the linear-gradient mixin since they are no longer needed with our latest and greatest browser (as per [annabeldunstone](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5762#note_14353141))  

## Are there points in the code the reviewer needs to double check?
None

## Why was this MR needed?
Reduces unnecessary CSS

## Screenshots (if relevant)
None

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
*  Closes #21558

See merge request !6063

Add white background for no readme container

## What does this MR do?
Changes the readme container background to white so that it is more consistent with the other default pages

## Are there points in the code the reviewer needs to double check?
Check for side effects but there really shouldn't be any

## Why was this MR needed?
Improves UI

## What are the relevant issue numbers?
Closes #20906 

## Screenshots (if relevant)
Before:
![Screen_Shot_2016-08-18_at_4.02.15_PM](/uploads/b3e70bba4c7ecab262bb4ff76bf80d85/Screen_Shot_2016-08-18_at_4.02.15_PM.png)

After:
![Screen_Shot_2016-08-22_at_4.30.41_PM](/uploads/520f276e1ed6786f66e3eff6e579b157/Screen_Shot_2016-08-22_at_4.30.41_PM.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5877

lib/backup: fix broken permissions when creating repo dir

## What does this MR do?

This MR fixes an issue where gitlab:backup:restore will not work because the repositories directory is set up with bad permissions. The bad permissions will prevent access to the repositories by the git user, causing all kinds of troubles (e.g. gitlab-shell won't install hooks).

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

Rake task gitlab:backup:restore would complete successfully, but gitlab:check will report errors and gitlab cannot access repos.

## Screenshots (if relevant)

* repositories.old.1472478726 was created without the fix
* repositories was created with the fix

![gitlab-repo-permissions](/uploads/6cf2de57fe4f1be0bd5b5e1a13234889/gitlab-repo-permissions.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

See merge request !6098

Add title to CI lint page

![Screen_Shot_2016-08-30_at_10.56.23](/uploads/651ce9e303b65854e96b18d301dcf1a3/Screen_Shot_2016-08-30_at_10.56.23.png)![Screen_Shot_2016-08-30_at_10.56.37](/uploads/77cb710971c4b84e659cbf9bbe13a1cb/Screen_Shot_2016-08-30_at_10.56.37.png)

See merge request !6100

Mention that the `:id` of a project can also be `NAMESPACE/PROJECT_NAME`

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/18936

See merge request !6102

[ci skip]

This commit fixes a typo where the mode argument to FileUtils.mkdir()
would be passed in decimal rather than octal format, yielding bad
permissions.

Ensure we update dropdown label after input has been added

Backport changes from https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/687

See merge request !5999

Change logo animation to CSS

## What does this MR do?
Converts the tanuki logo animation from javascript to CSS. You can now animate the tanuki svg logo by adding the CSS Class `animate`to it.

## Are there points in the code the reviewer needs to double check?
Just need to double check for browser compatibility

## Why was this MR needed?

*  Using CSS for simple animations is a best practice (Optimizes DOM, uses GPU to do animation rather than CPU)
*  Happy DOM 🎈 

## What are the relevant issue numbers?
Closes #20607 

## Screenshots (if relevant)
Before DOM
![8BrOJAqT4U](/uploads/705a3c7b53c45d32d435cafecfc958bd/8BrOJAqT4U.gif)

After DOM
![Screen_Shot_2016-08-03_at_10.30.08_PM](/uploads/e82d9b63501def4dc4e67a5659863680/Screen_Shot_2016-08-03_at_10.30.08_PM.png)

Before
![JnEgliIIVO](/uploads/39aaec48fd3e193f20cf455371ea2d13/JnEgliIIVO.gif)

After (Basically the same, hard to tell in my gif though because it was hard to get the timings right on the recording)
![fvLeXxmp3U](/uploads/058cf15fffed4be549af2e963eca4412/fvLeXxmp3U.gif)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5655

Remove unused mixins

## What does this MR do?
Remove unused mixins

## Are there points in the code the reviewer needs to double check?
None

## Why was this MR needed?
Reduces unused css

## Screenshots (if relevant)
Before:
```
$git grep 'btn-big' -- '*.scss'
app/assets/stylesheets/framework/mixins.scss:107:@mixin btn-big {

$git grep 'input-big' -- '*.scss'
app/assets/stylesheets/framework/mixins.scss:97:@mixin input-big {

$git grep 'solid-shade' -- '*.scss'
app/assets/stylesheets/framework/mixins.scss:45:@mixin solid-shade {

$git grep 'shade' -- '*.scss'
app/assets/stylesheets/framework/mixins.scss:41:@mixin shade {
app/assets/stylesheets/framework/mixins.scss:45:@mixin solid-shade {

$git grep 'linear-gradient' -- '*.scss'
app/assets/stylesheets/framework/buttons.scss:310:  background: linear-gradient(180deg, $white-light 25%, $gray-light 100%);
app/assets/stylesheets/framework/mixins.scss:20:@mixin linear-gradient($from, $to) {
app/assets/stylesheets/framework/mixins.scss:22:  background-image: -webkit-linear-gradient($from, $to);
app/assets/stylesheets/framework/mixins.scss:23:  background-image: -moz-linear-gradient($from, $to);
app/assets/stylesheets/framework/mixins.scss:24:  background-image: -ms-linear-gradient($from, $to);
app/assets/stylesheets/framework/mixins.scss:25:  background-image: -o-linear-gradient($from, $to);
app/assets/stylesheets/framework/nav.scss:11:  background: -webkit-linear-gradient($gradient-direction, rgba($gradient-color, 0.4), $gradient-color 45%);
app/assets/stylesheets/framework/nav.scss:12:  background: -o-linear-gradient($gradient-direction, rgba($gradient-color, 0.4), $gradient-color 45%);
app/assets/stylesheets/framework/nav.scss:13:  background: -moz-linear-gradient($gradient-direction, rgba($gradient-color, 0.4), $gradient-color 45%);
app/assets/stylesheets/framework/nav.scss:14:  background: linear-gradient($gradient-direction, rgba($gradient-color, 0.4), $gradient-color 45%);
app/assets/stylesheets/pages/diff.scss:167:        background-image: linear-gradient(45deg, #e5e5e5 25%, transparent 25%, transparent 75%, #e5e5e5 75%, #e5e5e5 100%),
app/assets/stylesheets/pages/diff.scss:168:        linear-gradient(45deg, #e5e5e5 25%, transparent 25%, transparent 75%, #e5e5e5 75%, #e5e5e5 100%);

$git grep 'border-radius-left' -- '*.scss'
app/assets/stylesheets/framework/mixins.scss:12:@mixin border-radius-left($radius) {

$git grep 'border-radius-right' -- '*.scss'
app/assets/stylesheets/framework/mixins.scss:16:@mixin border-radius-right($radius) {
```

After:
```
$git grep 'btn-big' -- '*.scss'
(nothing)

$git grep 'input-big' -- '*.scss'
(nothing)

$git grep 'solid-shade' -- '*.scss'
(nothing)

$git grep 'shade' -- '*.scss'
(nothing)

$git grep 'linear-gradient' -- '*.scss'
app/assets/stylesheets/framework/buttons.scss:310:  background: linear-gradient(180deg, $white-light 25%, $gray-light 100%);
app/assets/stylesheets/framework/nav.scss:11:  background: -webkit-linear-gradient($gradient-direction, rgba($gradient-color, 0.4), $gradient-color 45%);
app/assets/stylesheets/framework/nav.scss:12:  background: -o-linear-gradient($gradient-direction, rgba($gradient-color, 0.4), $gradient-color 45%);
app/assets/stylesheets/framework/nav.scss:13:  background: -moz-linear-gradient($gradient-direction, rgba($gradient-color, 0.4), $gradient-color 45%);
app/assets/stylesheets/framework/nav.scss:14:  background: linear-gradient($gradient-direction, rgba($gradient-color, 0.4), $gradient-color 45%);
app/assets/stylesheets/pages/diff.scss:167:        background-image: linear-gradient(45deg, #e5e5e5 25%, transparent 25%, transparent 75%, #e5e5e5 75%, #e5e5e5 100%),
app/assets/stylesheets/pages/diff.scss:168:        linear-gradient(45deg, #e5e5e5 25%, transparent 25%, transparent 75%, #e5e5e5 75%, #e5e5e5 100%);

$git grep 'border-radius-left' -- '*.scss'
(nothing)

$git grep 'border-radius-right' -- '*.scss'
(nothing)
```

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
Closes #21559

See merge request !6092

Keep committing ... spinner when conflict resolved

## What does this MR do?

When a conflict is resolved successfully, keep the 'committing ...' spinner until the new page loads rather than showing the standard button again, which is misleading. The old behaviour looks like this:

![Resolve_merge_conflict](/uploads/8e0efec0bb4b1358d4dd3353ea1dc57b/Resolve_merge_conflict.gif)

I don't think this needs a CHANGELOG entry as it's pretty minor.

See merge request !5892

Merge branch '21285-new-merge-request-source-and-target-branch-fields-filters-both-source-and-target-list' into 'master'

Fixed issue where filtering one dropdown will filter another on the page

## What does this MR do?

Moved `.option-hidden` to exist only in `SELECTABLE_CLASSES` as `NON_SELECTABLE_CLASSES` is used to re-show previously hidden elements.

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

## What are the relevant issue numbers?

Closes #21285.

## Screenshots (if relevant)

![2016-08-24_15.59.16](/uploads/8282bd6507d10de61097956a57bd63cc/2016-08-24_15.59.16.gif)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)
Closes #21285

See merge request !5985

Add body as data-container on pipeline graph tooltip

## What does this MR do?
Fixed data tooltip getting cut off

## What are the relevant issue numbers?
Closes #21070 

## Screenshots (if relevant)
![Screen_Shot_2016-08-23_at_8.45.42_AM](/uploads/87f072cfc2fdeced6161db6bec46320a/Screen_Shot_2016-08-23_at_8.45.42_AM.png)

See merge request !5955

Removes leading space from hover state in graph links

#### What are the relevant issue numbers?
Closes #21123 

#### Screenshots (if relevant)
![Screen_Shot_2016-08-24_at_8.35.15_AM](/uploads/2dc583391f87c6d0a67f0535967c637f/Screen_Shot_2016-08-24_at_8.35.15_AM.png)

See merge request !5980

Clarify steps when changing a document's location

Clarify the steps needed to change a document's location so issues like
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6024
don't occur.

See merge request !6070

[ci skip]

Make push events have equal vertical spacing.

## What does this MR do?

Evens out the vertical space between lines in push events.

## Are there points in the code the reviewer needs to double check?

Not afaik. 

## Why was this MR needed?

UI consistency.

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/19517

## Screenshots (if relevant)

Before: 
![Screen_Shot_2016-08-26_at_5.23.33_PM](/uploads/78e7a89912ec504d598f9bfec2a83eea/Screen_Shot_2016-08-26_at_5.23.33_PM.png)
After: 
![Screen_Shot_2016-08-26_at_5.23.16_PM](/uploads/3fa3e0902ef76b1e9c82e052842cd0ee/Screen_Shot_2016-08-26_at_5.23.16_PM.png)




## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [x] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

cc: @winniehell

See merge request !6055

First pass for community issue templates

## What does this MR do?

Includes community issue templates for Bugs and Feature Proposals.

In combination with a default Issue description template in the Project settings, we can advise the best places to find help and what is suitable to be posted to the CE issue tracker.

## Are there points in the code the reviewer needs to double check?

Verify that the templates are good

## Why was this MR needed?

To bring uniformity to the issues posted to the CE issue tracker

## What are the relevant issue numbers?

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

N/A

See merge request !5954

Fix branches page dropdown sort alignment

## What does this MR do?
Makes the dropdown sort top aligned with the other elements beside it

## Are there points in the code the reviewer needs to double check?
Shouldn't be

## Why was this MR needed?
Improves the UI

## What are the relevant issue numbers?
Closes #20837 

## Screenshots (if relevant)
Before:
![Screen_Shot_2016-08-11_at_10.08.56_AM](/uploads/d446c65276d856f6257921c0e662d110/Screen_Shot_2016-08-11_at_10.08.56_AM.png)
![Screen_Shot_2016-08-11_at_10.08.55_AM__2_](/uploads/015f0ac263281275405b127cd19718b4/Screen_Shot_2016-08-11_at_10.08.55_AM__2_.png)

After:
![Screen_Shot_2016-08-11_at_10.15.35_AM](/uploads/73a231d4e4d474b3cfbc6944ddd4f0e9/Screen_Shot_2016-08-11_at_10.15.35_AM.png)
![Screen_Shot_2016-08-11_at_10.08.36_AM__2_](/uploads/c5cda7911258766c02554f68ebd4bf82/Screen_Shot_2016-08-11_at_10.08.36_AM__2_.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5777

Fix due date example in slash commands documentation

## What does this MR do?

Fixes due data example in documentation for slash commands.

## Screenshots

Before:

![due_date_slash_commands_before](/uploads/63484bfcad6605e7caf2a98f39ae65d0/due_date_slash_commands_before.png)

After:

![slash_commands_brackets](/uploads/5a75563eb797b4d694c6e4eca946e17a/slash_commands_brackets.png)

See merge request !5931

Prevent .form-actions from leaking out of the container (originally by @pavelloz)

{+addition+} **This MR was originally by @pavelloz in !4889, the MR was inactive for 2 months and is a ~P3, I have credited @pavelloz in the `CHANGELOG`. The description below is also copied from that MR.**

## What does this MR do?
Fixes div width leaking outside  

## Are there points in the code the reviewer needs to double check?
Any place where it might been needed when introduced couple months ago.

## Why was this MR needed?

## What are the relevant issue numbers?
{+addition+}
Closes #18731.
## Screenshots (if relevant)
Before
![image](/uploads/f7bfb18a5949e95ab876f8c140ef1c91/image.png)
![image](/uploads/81d4f99ba3334f46f04bd078eefa2548/image.png)


After
![image](/uploads/f34b1e2bf4d8849275c206e66ccb8398/image.png)
![image](/uploads/2664adfcf00ca6831629a8fdab68f6f6/image.png)


## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

cc @jschatz1

See merge request !6075

Fix markdown help references

## What does this MR do?
Replaces all `markdown/markdown` references with `user/markdown` since `markdown/markdown.md` has been replaced with `user/markdown.md`

## Are there points in the code the reviewer needs to double check?
Shouldn't be any 😄 

## Why was this MR needed?
So that users who click on markdown help don't have to click/redirect to another link to get to the markdown help page

## What are the relevant issue numbers?
Closes #21434

## Screenshots (if relevant)
```
$git grep markdown/markdown
app/helpers/search_helper.rb:47:      { category: "Help", label: "Markdown Help",      url: help_page_path("markdown/markdown") },
app/views/admin/appearances/_form.html.haml:16:        Description parsed with #{link_to "GitLab Flavored Markdown", help_page_path('markdown/markdown'), target: '_blank'}.
app/views/help/ui.html.haml:552:  You can check how markdown rendered at #{link_to 'Markdown help page', help_page_path("markdown/markdown")}.
doc/development/doc_styleguide.md:425:[gfm]: http://docs.gitlab.com/ce/markdown/markdown.html#newlines "GitLab flavored markdown documentation"
doc/user/markdown.md:69:https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/markdown/markdown.md#newlines
doc/user/markdown.md:89:https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/markdown/markdown.md#multiple-underscores-in-words
doc/user/markdown.md:104:https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/markdown/markdown.md#url-auto-linking
doc/user/markdown.md:125:https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/markdown/markdown.md#multiline-blockquote
doc/user/markdown.md:159:https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/markdown/markdown.md#code-and-syntax-highlighting
doc/user/markdown.md:229:https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/markdown/markdown.md#inline-diff
doc/user/markdown.md:245:https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/markdown/markdown.md#emoji
doc/user/markdown.md:310:https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/markdown/markdown.md#task-lists
doc/user/markdown.md:333:https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/markdown/markdown.md#videos
doc/user/markdown.md:783:[markdown.md]: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/markdown/markdown.md
spec/routing/routing_spec.rb:110:    path = '/help/markdown/markdown.md'
spec/routing/routing_spec.rb:112:                                  path: 'markdown/markdown',
```

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !6024

[ci skip]