Block concurrent pipeline processings

## What does this MR do?

It's possible that two builds that succeed at the same will try to
concurrently process pipeline. This can lead to scenario when it will
fail to trigger next stages.

This MR makes sure that process of updating is blocking.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/21263

See merge request !6090

API: Expose issue confidentiality flag.

## What does this MR do?

This MR adds support for confidential issues the the API. The property as exposed and users can create or update confidential issues.

## What are the relevant issue numbers?

Closes #17199 

See merge request !5384

The ID of a project can be also a string

## What does this MR do?

Add the integer type for the project's ID in the API docs.

## What are the relevant issue numbers?

Missed a few spots in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6102

See merge request !6133

[ci skip]

Minor code refactor for inlining functions in logo JS.

See merge request !6097

Create bitmaps during 'git gc'

## What does this MR do?

Add instructions to enable creation of Git packfile bitmaps.

## Why was this MR needed?

Because we still are not using Git packfile bitmaps in GitLab

[ci skip]

See merge request !6104

Don't expose a user's private token in the `/api/v3/user` API

## Why was this MR needed?

A user's private token is being leaked in the `/api/v3/user` API.

## What are the relevant issue numbers?

- Closes #20911

## Does this MR meet the acceptance criteria?

- [ ]  #20911 !6047 Application-Specific Tokens Are Insecure
    - [x]  Implementation
    - [x]  Test
    - [x]  CHANGELOG
    - [x]  Make sure build is green
    - [x]  Assign to endboss
    - [ ]  Wait for merge


See merge request !6047

Allow setting branch refs for MR

@dbalexandre can you take a look please?

See merge request !6025

Added performance guidelines for new MRs

## What does this MR do?

This MR adds a set of guides that should be followed by merge request authors.

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

Spelling, grammar, etc

## Why was this MR needed?

There is no set of guidelines one should follow when submitting merge requests. This leads to developers at times disregarding performance. This in turn results in performance specialists having to clean up the mess, or production engineers being woken up in the middle of the night because the database is on fire.

## Does this MR meet the acceptance criteria?

- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- 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)

cc @DouweM @rspeicher @pcarranza @dzaporozhets 

See merge request !5905

Remove redundant pipeline tooltips from short labels

## What does this MR do?
Removes the tooltips from labels that have less than 12 characters, so that the tooltips only show when the pipeline labels are truncated

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

## Why was this MR needed?
Removes unnecessary tooltips for non-truncated pipeline labels

## Screenshots (if relevant)
Before:
![NjBCzZ63NK](/uploads/2c5627f3000ceeeb134452a6619734f2/NjBCzZ63NK.gif)

After:
![EHsGdjGi3F](/uploads/ffdc6f9c8e807ca4eaf576ee6a660798/EHsGdjGi3F.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)

## What are the relevant issue numbers?
#21542

See merge request !6058

- This would allow anyone with a personal access token (even a read-only
  token, once scopes are implemented) to escalate their access by
  obtaining the private token.

Remove not-null constraint on lock_version column if it exists

Closes #21678

See merge request !6118

Check for pipelines when setting page_gutter_class.

## What does this MR do?

Fixes regression issue related to the MR window sliding behind the right sidebar on page refresh. 

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

I'm getting stuck thinking about if/how to test this. Or maybe it just deserves a note somewhere about remembering to update `page_gutter_class` when a new route is added?

## Why was this MR needed?

This regression prevented users from using many features of the MR view.

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/21121

## Screenshots (if relevant)

Before: 
![Screen_Shot_2016-08-23_at_11.08.04_AM](/uploads/bad1a83569022a7fc699a978c5abef62/Screen_Shot_2016-08-23_at_11.08.04_AM.png)

After: 
![Screen_Shot_2016-08-23_at_11.07.46_AM](/uploads/6cbcb2f849c68dfc93d8a4b53089b06e/Screen_Shot_2016-08-23_at_11.07.46_AM.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
  - [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 !5952

Added search for all lists on issue boards

## What does this MR do?

Adds a search box to allow the user to search all lists in issue boards rather than just the backlog.

## Screenshots (if relevant)

![Screen_Shot_2016-08-30_at_10.33.15](/uploads/67e96055d60a9b3209ce3831a1980c09/Screen_Shot_2016-08-30_at_10.33.15.png)

![Screen_Shot_2016-08-30_at_10.33.19](/uploads/8d5253b8f2ecf1cf9a69d70be8ccf1f9/Screen_Shot_2016-08-30_at_10.33.19.png)

## What are the relevant issue numbers?

Closes #21139

See merge request !6101

Closes #21678

Added project specific enable/disable setting for LFS

## What does this MR do?

Adds project specific enable/disable setting for LFS

## What are the relevant issue numbers?

Needed for #18092

See merge request !5997

Resize created icon

## What does this MR do?
Resizes `created` SVG

## Why was this MR needed?
Because:
![Screen_Shot_2016-08-30_at_3.33.38_PM](/uploads/c4c987e323b4c9cedeb298f08abbc307/Screen_Shot_2016-08-30_at_3.33.38_PM.png)

Hard-coding in the size into the SVG isn't a great solution, but we've got a bit of technical debt here. All the other icons are sized this way, so for this patch fix I think we should just match it. Ideally we'll have classes directly in the SVG code so we can target all these icons properly, and do all color/sizing through CSS

## Screenshots (if relevant)
![Screen_Shot_2016-08-30_at_3.35.49_PM](/uploads/35cf6372142b45b708b6757ea965c075/Screen_Shot_2016-08-30_at_3.35.49_PM.png)

See merge request !6114

prevent authored awardable thumbs  votes

## What does this MR do?
This MR should prevent users from upvoting or downvoting   issues/merge requests/notes authored by them. 

## What are the relevant issue numbers?
Closes #20913 

See merge request !5841

Fix CHANGELOG

Remove duplicate 8.11.4 entries and mark 8.11.3 as released.

[ci skip]

See merge request !6116

Remove duplicate 8.11.4 entries and mark 8.11.3 as released.

[ci skip]

Remove default value for lock_version

## What does this MR do?

From the very beginning we added `lock_version` column with default value, then we reverted that MR. A bit later we added that migration again but column's default value has been removed from migration. So if you installed GitLab form master it's possible that you have default value, which caused  the bug.

We don't need to change a CHANGELOG here I think.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/21527 and https://dev.gitlab.org/gitlab/organization/issues/971

See merge request !6111

Drop unused CI tables and files

See merge request !6014

docs: make sure to update 8.10-to-8.11 workhorse version too (see !5983)

## What does this MR do?

Make sure to remember the correct workhorse version for specific version update instructions for those of us still doing source installs.
Related to !5983.

See merge request !6049