Remove redundant mixins

## What does this MR do?
Removes the following redundant mixins
```
@mixin box-shadow($shadow) {
  box-shadow: $shadow;
}

@mixin border-radius($radius) {
  border-radius: $radius;
}
```

## Are there points in the code the reviewer needs to double check?
Just need to make sure the refactor didn't break anything. Last time I did something like this, we faced an edge case where values `.5` would pass correctly in mixins but not when passed directly to the property.

## Why was this MR needed?

*  Reduces redundant code which leads to happier developers 😄 

## 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 [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 #22012

See merge request !6287

Add link to test coverage report to README

## What does this MR do?

Since we have GitLab Pages with test coverage report, it makes sense to link coverage badge there, instead of linking to commits page.

See merge request !6772

Rename HTMLEntityFilter to HtmlEntityFilter to fix autoloading

See merge request !6776

Use user from let instead recreate in before

## What does this MR do?
It`s minor fix in tests. We can use factory from let instead recreate user before each test.
 
## Are there points in the code the reviewer needs to double check?
No

## Why was this MR needed?

## Screenshots (if relevant)
No

## 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
  - [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 it does - rebase it please)
- [ ] [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 !6762

Improve backup doc readability

From https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3761

See merge request !6781

[ci skip]

Explain the extra chmod

There is confusion about what passing `0600` to File.open does.

```
$ touch /tmp/foobar
$ ls -l /tmp/foobar
-rw-r--r--  1 jacobvosmaer  wheel  0 Sep 26 14:20 /tmp/foobar
$ ruby -e 'File.open("/tmp/foobar", "w", 0600)'
$ ls -l /tmp/foobar
-rw-r--r--  1 jacobvosmaer  wheel  0 Sep 26 14:20 /tmp/foobar
$ 
$ 
$ rm /tmp/foobar
$ ruby -e 'File.open("/tmp/foobar", "w", 0600)'
$ ls -l /tmp/foobar
-rw-------  1 jacobvosmaer  wheel  0 Sep 26 14:21 /tmp/foobar
```

See merge request !6523

Changes to make Git basics more intuitive

From https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6420

See merge request !6777

- updated verbiage where appropriate
- changed "git config" commands to include quotes for variables to be more in line with standard practive and to avoid issues with spaces
- updated CHANGELOG as part of commit

Remove Ci::ApplicationController.

See gitlab-org/gitlab-ce!6757.

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

Clarify which token should be used to delete a Runner



See merge request !6775

Fix ci pipeline processing with async jobs

## What does this MR do?

This MR fixes CI pipeline processing with asynchronous jobs called from `around_transition` provided by state machine.
For details see  https://github.com/pluginaweek/state_machine/issues/191 and commit f68acbac.

## Why was this MR needed?

Recently merged https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6650 introduced problem with asynchronous job being deployed when `around_transition` still held transaction, which caused race condition that prevented pipeline status to change in a proper way. 

## What are the relevant issue numbers?

Closes #23111

See merge request !6736

Correct namespace validation to forbid bad names #21077

## What does this MR do?
Updates master namespace regex to forbid any namespace ending in `.git` or `.atom` and corrects and adds relevant tests

## Are there points in the code the reviewer needs to double check?
I think it's all good. I could use help with the creation of tests for usernames with trailing `.atom` or `.git` as the testing framework is a bit over my head.

## Why was this MR needed?
A group that ends in `.atom` will cause the relevent dashboard to crash if the user (ANY user, not just the creator) has visibility of the group until it is deleted through the admin panel (it cannot be renamed, the edit page will crash. It may be fixable through the API, that wasn't checked.)

This allows a malicious user with group creation privileges to bulk add users to a group, rename the group to a bad name, and crash the groups dashboard for all members of the group. The same applies if the group is internal or public and users navigate to the explore tab of the groups dashboard.

The same applies to usernames ending in `.atom`.

In many places of the code, it implies that `.git` in not allowed at the end of namespaces, but many allowed it anyway. This MR forbids it everywhere to prevent potential issues (like the one with `.atom` going forward).

## What are the relevant issue numbers?
Group path validation incomplete, crashes groups dashboard #21077

## 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)

See merge request !5994

Fix a typo in doc/api/labels.md

See merge request !6760

Fix wrong icon in CI build detail sidebar: right-arrow => arrow-right

## What does this MR do?

It fixes a wrong icon name in the build detail page's sidebar: `right-arrow` should be `arrow-right`!

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

No.

Closes #23123

See merge request !6768

Prevent running GfmAutocomplete setup for each diff note

## What does this MR do?

Debounces GfmAutoComplete.setup.

## Why was this MR needed?

See https://gitlab.com/gitlab-org/gitlab-ce/issues/22704

Major lag on MR screens with many diff notes.

## 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
  - [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?
https://gitlab.com/gitlab-org/gitlab-ce/issues/22704

See merge request !6569

Make searching for commits case insensitive.

## 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
  - [ ] 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?

Fixes #21800

See merge request !6715

Update Gitlab Shell to fix errors moving projects between storages

## What does this MR do?

Update Gitlab Shell to fix errors moving projects between storages

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

No

## Why was this MR needed?

We are unable to move projects using `ionice` because of an error in the current version of gitlab-shell. This brings the changes of https://gitlab.com/gitlab-org/gitlab-shell/merge_requests/96 and https://gitlab.com/gitlab-org/gitlab-shell/merge_requests/97

## 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 [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] 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 it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Related to https://gitlab.com/gitlab-com/infrastructure/issues/513

See merge request !6751

Try tmpfs for repository storage, etc

See merge request !6730

Improve project policy specs

See merge request !6442

reword title for issues_controller#show and issues_controller#edit

Closes #21712

See merge request !6503

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

Prevent conflict b/w search field and its dropdown

What does this MR do?

Stops the global search form's default "action" from fighting with
dropdown items when using the keyboard to navigate the dropdown.
`e.preventDefault()` is now called on the enter key when a dropdown item
is already selected.

Closes #22872

See merge request !6643

Stop the global search form's default "action" from fighting with
dropdown items when using the keyboard to navigate the dropdown.
`e.preventDefault()` is now called on the enter key when a dropdown item
is already selected.
Signed-off-by: Rémy Coutable <remy@rymai.me>

Fixes #21800.