Network page appear with an error message when entering nonexistent git revision

Closes #2362

See merge request !7172

Replace trigger with the new ID of the docs project

Now that the old docs site is deprecated in
favor of https://gitlab.com/gitlab-com/gitlab-docs

See merge request !7343

[ci skip]

17492 Update link color for more accessible contrast

## What does this MR do?
Improves contrast of links to pass accessibility contrast checker http://webaim.org/resources/contrastchecker/

## Screenshots (if relevant)
Before:
![Screen_Shot_2016-11-07_at_11.09.44_AM](/uploads/233c53cd81436a00f0cc7f826ca900df/Screen_Shot_2016-11-07_at_11.09.44_AM.png)
After:
![Screen_Shot_2016-11-07_at_11.09.22_AM](/uploads/698ac990d61434893709a3cea78896d9/Screen_Shot_2016-11-07_at_11.09.22_AM.png)

## Does this MR meet the acceptance criteria?

- [ ] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) 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?


Closes #17492

See merge request !7340

Rewritten spinach git_blame tests to RSpec feature tests

Part of #23036. This MR contains 'git blame' feature tests rewritten in RSpec.
 
See merge request !7197

Use the Gitlab Workhorse HTTP header in the admin dashboard

Fixes issue #21664 where the GitLab Workhorse version displayed within the Admin Area was not correct for installations from source.

See merge request !7332

Upgrade redis-rails from 4.0.0 to 5.0.1.

This updates redis-rails to 5.0.1 along with its dependencies. I helped upgrade redis-actionpack so it would work with both Rails 4.2 and 5.0 in the same version.

Unfortunately none of the gems have Changelogs :/

- redis-rails: https://github.com/redis-store/redis-rails
- redis-actionpack: https://github.com/redis-store/redis-actionpack
- redis-activesupport: https://github.com/redis-store/redis-activesupport
- redis-rack: https://github.com/redis-store/redis-rack
- redis-store: https://github.com/redis-store/redis-store

Working toward #14286.

See merge request !7291

Expose Label id to API

Closes #23448

See merge request !7275

Processing Commits Using Sidekiq

This moves the code  of `GitPushService#process_commit_messages` into a separate Sidekiq worker. This allows processing of commits to happen in parallel, speeding up the process. See the individual commit (messages) for more information.

Part of https://gitlab.com/gitlab-org/gitlab-ce/issues/15463

See merge request !6802

Add missing security specs for raw snippet access

## What does this MR do?
It extends the project snippets access security specs to cover raw snippet paths as well.

When I was researching snippets for !7256, I noticed that specs existed for the HTML show view of project snippets but not the raw view. Seeing as this is a spec that is checking for access regressions on places where sensitive information might be kept, I thought it would be a good idea to cover the raw snippets access too.

To balance out the karma of adding in extra tests I also changed the tests to all use an `empty_project` spec.

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

With the aim of making the specs easier to read, I restructured some of them to use context blocks for each type of snippet.

I've used the same access rights defined for the show snippet paths for the raw snippet access. 

## Why was this MR needed?

To catch security regressions on raw snippet access for projects.

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [-] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) 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 [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)
- [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 !7300

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

Fixing rubocop violations

Relocated git_blame spec and fixed styling issue

Rewritten spinach git_blame tests to rspec feature tests

Fixing rubocop violations

Relocated git_blame spec and fixed styling issue

Rewritten spinach git_blame tests to rspec feature tests

Fixing rubocop violations

Rewritten spinach git_blame tests to rspec feature tests

Fixing rubocop violations

Rewritten spinach git_blame tests to rspec feature tests

Fixing rubocop violations

Relocated git_blame spec and fixed styling issue

[e44da1c] Add Label API expected keys to tests

[ac929c8] Update Label API documentation

Use `git update-ref --stdin -z` to speed up TestEnv.set_repo_refs

See merge request !7283

Use more than one kind of Git garbage collection

Replaces https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6588 by @jacobvosmaer to get the builds to pass :)

Closes #22729

See merge request !7321

This moves the code used for processing commits from GitPushService to
its own Sidekiq worker: ProcessCommitWorker.

Using a Sidekiq worker allows us to process multiple commits in
parallel. This in turn will lead to issues being closed faster and cross
references being created faster. Furthermore by isolating this code into
a separate class it's easier to test and maintain the code.

The new worker also ensures it can efficiently check which issues can be
closed, without having to run numerous SQL queries for every issue.

This class can be used to reduce a list of issues down to a subset based
on user permissions. This class operates in such a way that it can
reduce issues using as few queries as possible, if any at all.

These specs use raw Redis objects which can not use the memory based
caching mechanism used for tests. As such we have to explicitly flush
the data from Redis before/after each spec to ensure no data lingers on.

This method returns the project's ID, making ExternalIssue slightly more
compatible with Issue (which also defines the "project_id" method).

This method can be used to retrieve a list of projects for a user that
said user has reporter access to. This list is then be reduced down to
a specific set of projects. This allows you to reduce a list of projects
to a list of projects you have reporter access to in an efficient
manner.

Fixups to "Round-robin repository storage"

## What does this MR do?

* Simplifies a method in application_settings.rb
* Correctly marks a migration as needing downtime
* Documents the requirement for renamed columns to be 

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

Should any of these changes be split out? Ideally we'd get this into the same point release as !7273

## Why was this MR needed?

Post-facto review of !7273

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) 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
  - [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 it does - 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?

Related to #24059

/cc @yorickpeterse @rspeicher

See merge request !7287

Previously, we were calling `git update-ref <ref> <sha>` about 30 times per
test using `create(:project)` or similar.

Add an index for project_id in project_import_data to improve

See merge request !7316

Refactor template selector in issuable form

CE brother of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/844

See merge request !7249

Use method helper instead of add_template_helper

On my opinion, better to use method `helper` instead of `add_template_helper`.
Maybe there is reason doing it here. could you please explain if yes?
Thanks!

See merge request !7315

Exposes the label priority to the API. Furthermore, it allows the user to modify the priority via the API.

Closes #21269

See merge request !7286

Fix broken link to observatory cli on Frontend Dev Guide

See merge request !7317

performance

We see that many slow queries on GitLab.com are dominated by finding
the project import data for a specific project. Adding an index is
the most straightforward way of fixing this.

Closes #23748