See broken build here: https://gitlab.com/gitlab-org/gitlab-ee/builds/3763020

Refactor merge requests documentation

## What does this MR do?

Add more information on merge requests. CE https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6202

## Moving docs to a new location?

See the guidelines: http://docs.gitlab.com/ce/development/doc_styleguide.html#changing-document-location

- [x] Make sure the old link is not removed and has its contents replaced with a link to the new location.
- [x] Make sure internal links pointing to the document in question are not broken.
- [x] Search and replace any links referring to old docs in GitLab Rails app, specifically under the `app/views/` directory.
- [x] If working on CE, submit an MR to EE with the changes as well.

See merge request !716

https://gitlab.com/gitlab-org/gitlab-ee/commit/0ec82b0a148d626bfe84135d57fd95f3d7d209b0

API: Restore backward-compatibility for POST /projects/:id/members when membership is locked

Closes #971.

/cc @rdavila

See merge request !715

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

Conflicts:
	db/schema.rb
	doc/workflow/README.md
	spec/models/repository_spec.rb

Move CHANGELOG entries of !5361, !5451 and !5887 from 8.11 to 8.12

## What does this MR do?

Move CHANGELOG entries of !5361, !5451 and !5887 from 8.11 to 8.12

## Why was this MR needed?

They were wrongly added to 8.11 here:

- https://gitlab.com/gitlab-org/gitlab-ce/commit/220755f52ad6e3fdfa43c62e0a4a4051721246dc#note_14900001
- https://gitlab.com/gitlab-org/gitlab-ce/commit/87f93ceb9542c415d6c23c72ff93d63272107d54

See merge request !6189

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

Fix missing flash messages on service edit page

## What does this MR do?

This MR fixes missing post-update flash notifications for service edit page. Bug was introduced in https://gitlab.com/gitlab-org/gitlab-ce/commit/76aad9b76ed756ca9ba2cbcdb399c815e542b3ae#3ca7aff54d2814b971a98a7bf2837e07ab3dfa04_21_20 and caused by passing `notice: Successfully updated.` to path helper instead of passing it to `redirect_to` due to wrong parenthesis placement.

## Why was this MR needed?

While adding HipChat integration I noticed that no messages are being displayed after clicking on "Save changes" button. I looked into code and observed that there is a code for these messages which once worked but doesn't work anymore. It's a regression which should be fixed.

## Screenshots (if relevant)

![image](/uploads/32b851e5bdc2a6438f35061473db9650/image.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [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 !6195

Safer ref updates

Use `git update-ref` to prevent clobbering concurrent ref updates. If
rugged/libgit2 is temporarily confused, due to concurrent `git gc` for
example, then it used to be possible to accidentally reset a ref to an
earlier state and lose commits. Because `git update-ref` does not get
confused by `git gc`, what will happen now is that the commit based on
confused information fails, preventing data loss.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/20353

See merge request !6130

Add documentation on template dropdowns

CE https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4865

See merge request !710

Add documentation on template dropdowns

## What does this MR do?

Add docs for the dropdown template selectors

/cc @axil 

See merge request !4865

Update README.md

Added a line to the SSH Key Gen section, to ensure that the `before_script` does not prompt for a passphrase.

See merge request !6176

Add link on API docs index page



See merge request !6190

Fix randomly failing specs in expand_collapse_diff_spec:

This MR fixes the following random failure in a spec:

```
 Failure/Error: namespace.human_name + ' / ' + name

     ActionView::Template::Error:
       undefined method `+' for nil:NilClass
     # ./app/models/project.rb:807:in `name_with_namespace'
     # ./app/views/layouts/project.html.haml:1:in `_app_views_layouts_project_html_haml___2918737809244135908_70160161538920
'
     # ./app/controllers/projects/commit_controller.rb:23:in `show'
     # ./lib/gitlab/request_profiler/middleware.rb:15:in `call'
     # ./lib/gitlab/middleware/go.rb:16:in `call'
     # ./lib/gitlab/middleware/static.rb:9:in `call'
     # ------------------

     # --- Caused by: ---
     # NoMethodError:
     #   undefined method `+' for nil:NilClass
     #   ./app/models/project.rb:807:in `name_with_namespace'
```

Capybara's `click_link` method doesn't actually wait for the page to reload.
When the `expand_all_diffs` parameter is used, we need to search for unique
elements that appear to ensure that the page has actually reloaded.

Closes #21841

See merge request !6193

```
 Failure/Error: namespace.human_name + ' / ' + name

     ActionView::Template::Error:
       undefined method `+' for nil:NilClass
     # ./app/models/project.rb:807:in `name_with_namespace'
     # ./app/views/layouts/project.html.haml:1:in `_app_views_layouts_project_html_haml___2918737809244135908_70160161538920
'
     # ./app/controllers/projects/commit_controller.rb:23:in `show'
     # ./lib/gitlab/request_profiler/middleware.rb:15:in `call'
     # ./lib/gitlab/middleware/go.rb:16:in `call'
     # ./lib/gitlab/middleware/static.rb:9:in `call'
     # ------------------

     # --- Caused by: ---
     # NoMethodError:
     #   undefined method `+' for nil:NilClass
     #   ./app/models/project.rb:807:in `name_with_namespace'
```

Capybara's `click_link` method doesn't actually wait for the page to reload.
When the `expand_all_diffs` parameter is used, we need to search for unique
elements that appear to ensure that the page has actually reloaded.

Closes #21841

[ci skip]

Conflicts:
	app/assets/javascripts/project_new.js
	app/views/projects/_merge_request_settings.html.haml
	spec/javascripts/datetime_utility_spec.js.coffee

Remove suggested colors hover underline

## What does this MR do?
* Removes the blue hover underline for the suggested color containers 
* Added `cursor: pointer` to the suggested color containers  

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

## Why was this MR needed?
Improves UI

## Screenshots (if relevant)
Before:
![DS48AvgSVX](/uploads/0077e7a5837c8ce9fe2493ad6a42a018/DS48AvgSVX.gif)

After:
![olZzS68WNr](/uploads/4e0ae808c69942a528f1303df8cddeae/olZzS68WNr.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 [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [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 #21792

See merge request !6165

Fix alignment of icon buttons

## What does this MR do?

Fix misalignment of buttons with only an icon which was introduced by !5451.

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5451#note_14066627

## Screenshots

### Before

![with-text](/uploads/aa7f7a98e2015070689e762e0cf99844/witht-text.png)

![without-text](/uploads/72db7c54e3961fd0df34b0ea79455fd0/without-text.png)

### After

![with-text](/uploads/3f19e55773083bcb22f3909f6dc0d147/witht-text.png)

![without-text](/uploads/b6647d4d71eb5cd9d1712908d2b93665/without-text.png)


See merge request !5887