Fixes bulk-assign label for multiple issues not having the same labels

## What does this MR do?
Fixes a bug when bulk-assigning a label to multiple issues while the label is present in on the issues on the selection.

## Screenshots (if relevant)

**Before Bugfix**

<img src="/uploads/ad1f290bcf3930177a3a71c69cbe5325/before-bugfix.gif" width="700"/>

**After Bugfix**

<img src="/uploads/1f04d6bf027806fb13ca3773febda744/bugfix.gif" width="700"/>

## Does this MR meet the acceptance criteria?

- [x] Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)

See merge request !4602

Added when to artifacts

The syntax for this will be:

```
job:
  artifacts:
    when: on_failure
```

cc @grzesiek @tmaczukin 

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/4034


See merge request !4201

Cache only apt and ruby from vendor

## What does this MR do?

Optimises caching mechanism when testing gitlab-ce/ee repositories.


See merge request !4619

Instrument all Banzai::ReferenceParser classes

## What does this MR do?

This MR instruments all the classes in the `Banzai::ReferenceParser` namespace.

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

No.

## Why was this MR needed?

The classes in question weren't instrumented meaning we have no idea how they're performing in production.

## What are the relevant issue numbers?

None.

## 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] 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 !4620

Add guide on changing a document's location

## What does this MR do?

Add a documentation styleguide when changing a document's location.

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/3349


See merge request !4624

Change to new Notes styleguide



See merge request !4625

[ci skip]

[ci skip]

Fix migration helper race conditions

## What does this MR do?

This MR fixes two problems with the migration helpers:

1. An error in `change_column_null` would not drop the previously created column
2. `update_column_in_batches` would rely on the number of rows in a table to determine how many to update. This meant that newly inserted rows (after the `COUNT`) would not be taken into account.

This MR also removes an outdated comment for `update_column_in_batches`.

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

No.

## Why was this MR needed?

See above.

## What are the relevant issue numbers?

Fixes #18483

## Does this MR meet the acceptance criteria?

- [ ] [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)
- [ ] ~~API support added~~
- [ ] Tests
  - [x] 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)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4618

Only show branches for revert / cherry-pick

## What does this MR do?

Stop showing tags in the revert and cherry-pick select options. You can't change a tag anyway.

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

Uncertain.

## Why was this MR needed?

Showing tags doesn't make any sense and will just throw an exception if the user tries to cherry-pick or revert onto a tag.

## What are the relevant issue numbers?

Fixes #18377.

## Screenshots (if relevant)

On the GitLab CE repo:

![image](/uploads/9c5a6f09300a7c46d0a794bef2956992/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
  - [ ] 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 !4596

Change logs.md location in README

## What does this MR do?

Forgotten link from https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4622

See merge request !4623

Move logs/logs.md to administration/logs.md

## What does this MR do?

Move `logs.md` documentation under `administration/` where it fits better.

## Why was this MR needed?

For a better doc structure.

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/3349

See merge request !4622

[ci skip]

Remove notification level from user model

part of #3359 

See merge request !4494

[ci skip]

Tags are immutable, so we can't add a commit to either revert or
cherry-pick another commit to them.

Now that this code is no longer part of Banzai::Filter it needs to be
instrumented explicitly.

Instead of updating a fixed number of rows (based on the amount of rows
available at the start of the update) the method
"update_column_in_batches" will now continue updating rows until it runs
out of rows to process.

For a table with a high rate of inserts this may result in the migration
taking quite some time. However, the alternative is not all rows being
updated or the "change_column_null" method raising an error due to there
being NULL values.

This ensures that whenever changing the NULL constraint of a column
fails we still drop the column.

Merge branch '18446-when-this-merge-request-is-accepted-this-issue-will-be-closed-automatically-rendered-twice' into 'master'

Resolve ""When this merge request is accepted, this issue will be closed automatically" rendered twice"

## What does this MR do?

1. Only show the above text when there is an MR that will close the issue, and even then, only show it once.
2. Apply 98f147e84d2bd8f2278452ac0852118452c76d4a to a bunch of other places that need it.

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

¯\_(ツ)_/¯

## Why was this MR needed?

Some pages were broken.

## What are the relevant issue numbers?

Fixes #18446.

## Screenshots (if relevant)

Before:
![image](/uploads/23cfaf95b7c798f22963ff67f78a803b/image.png)

After:
![image](/uploads/ca9c538069ba52e53858c69387738521/image.png)

## 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)

See merge request !4594

Improve SVG sanitizer to handle namespaced attributes

* Small refactor in the SVG sanitizer
* Enable already whitelisted namespaced attributes to be allowed
* Disable `xlink:href`to reference any external resource

Fixes #18100 

See merge request !4427

Since introduction of gitignore the vendor folder contains also gitignores which affects detection when to update a cache.
We explicitly cache only apt and ruby folders.

Fix Error 500 when using closes_issues API with an external issue tracker

Closes #18484

See merge request !4608

Closes #18484

Improvements to offscreen navigation

Improvements on top of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4579 based on mockups from https://gitlab.com/gitlab-org/gitlab-ce/issues/18417#note_12389766

See merge request !4607

Resolve "Hide Left sidebar paradigm"

## What does this MR do?
Hides the nav bar by default & centers the tanuki logo in the top nav

## Why was this MR needed?
UX

## What are the relevant issue numbers?
Closes #18417 

## Screenshots (if relevant)
![Screen_Shot_2016-06-10_at_12.49.10_PM](/uploads/c281e4c9de1c1bc9af59ebfa8d2bd18b/Screen_Shot_2016-06-10_at_12.49.10_PM.png)
![Screen_Shot_2016-06-10_at_12.49.27_PM](/uploads/635e0a88230105faa5527f6632899ddb/Screen_Shot_2016-06-10_at_12.49.27_PM.png)
<img src="/uploads/3001a9c723037012f1b86cfacfb1225e/Screen_Shot_2016-06-10_at_12.51.41_PM.png" width="500px">

See merge request !4579

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Fixed search form padding

## What does this MR do?

Corrects the padding of the search form.

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

Ney.

## Why was this MR needed?

UX

## What are the relevant issue numbers?

Closes #18463.

## Screenshots (if relevant)

![Screen_Shot_2016-06-10_at_14.07.32](/uploads/e4d127c66cf7fa3286279367d6e4ea7c/Screen_Shot_2016-06-10_at_14.07.32.png)

## 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
- [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 !4591

Fixes the case when we want to assign a label to multiple issues and one of the issues has already the label we want to apply.