Make new tabs persistent when changing view.

## What does this MR do?

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

## Why was this MR needed?

## What are the relevant issue numbers?

## Screenshots (if relevant)

## 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)

cc @stanhu @DouweM @rdavila 

See merge request !5859

Send notification emails when users are newly mentioned in issue or MR edits

## What does this MR do?

Introduces "new mention in issue" and "new mention in MR" email notifications.  Editing a Mentionable title or description and adding a mention to a user who was not previously mentioned will now send them a notification email, following usual permissions for doing so.

## Why was this MR needed?

Issues & MRs may be edited to include mentions to new people. We don't currently send out email notifications of these edits to anyone, although they do create TODOs. This brings email notifications into parity with TODOs.

## What are the relevant issue numbers?

Closes #2451

See merge request !5800

Hide "Create new list button" on Issues and MRs pages

![1](/uploads/d8b08cb62cfc9e9d29e3e64b2ed0a8af/1.png)

/cc @jschatz1 

See merge request !5852

Eliminate unneeded calls to Repository#blob_at when listing commits with no path

See merge request !5848

Added VueJS plugin

## What does this MR do?

Adds the VueJS & Vue resource plugin with environment detection. 

## What are the relevant issue numbers?

Closes #20738 

See merge request !5845

Fix downtime check formatting

## What does this MR do?

This MR adjusts the formatting of the migration downtime checker so messages are more readable.

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

Not specifically

## Why was this MR needed?

Formatting was somewhat hard to read and the online/offline indicators used the wrong colour.

## New Format

```
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20140407135544_fix_namespaces.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160705054938_add_protected_branches_push_access.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160705054952_add_protected_branches_merge_access.rb
[offline]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160705055254_move_from_developers_can_merge_to_protected_branches_merge_access.rb:

We're creating a `merge_access_level` for each `protected_branch`. If a user creates a `protected_branch` while this
is running, we might be left with a `protected_branch` _without_ an associated `merge_access_level`. The `protected_branches`
table must not change while this is running, so downtime is required.

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5081#note_13247410

[offline]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160705055308_move_from_developers_can_push_to_protected_branches_push_access.rb:

We're creating a `push_access_level` for each `protected_branch`. If a user creates a `protected_branch` while this
is running, we might be left with a `protected_branch` _without_ an associated `push_access_level`. The `protected_branches`
table must not change while this is running, so downtime is required.

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5081#note_13247410

[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160705055809_remove_developers_can_push_from_protected_branches.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160705055813_remove_developers_can_merge_from_protected_branches.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160716115711_add_queued_at_to_ci_builds.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160725083350_add_external_url_to_enviroments.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160727163552_create_user_agent_details.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160728081025_add_pipeline_events_to_web_hooks.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160728103734_add_pipeline_events_to_services.rb
[offline]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160729173930_remove_project_id_from_spam_logs.rb:

Removing a column that contains data that is not used anywhere.

[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160801163709_add_submitted_as_ham_to_spam_logs.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160802010328_remove_builds_enable_index_on_projects.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160805041956_add_deleted_at_to_namespaces.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160810102349_remove_ci_runner_trigram_indexes.rb
[online]: /home/yorickpeterse/Projects/gitlab/gitlab-ce/db/migrate/20160810142633_remove_redundant_indexes.rb
```

## Does this MR meet the acceptance criteria?

- 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 !5840

Tracking of custom events

## What does this MR do?

This MR adds the ability to track custom events such as the number of Git pushes.

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

The usual stuff.

## Why was this MR needed?

We want to track more business level data such as the number of Git pushes, how many repositories are imported (and from where), etc.

## What are the relevant issue numbers?

gitlab-org/gitlab-ce#13720

## 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
  - [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)

cc @pcarranza 

See merge request !5830

Move to project dropdown with infinite scroll for better performance

See merge request !5828

Backport changes from gitlab-org/gitlab-ee!581

## What does this MR do?

Backports changes that were made in gitlab-org/gitlab-ee!581, to avoid potential merge conflicts in the future.

## What are the relevant issue numbers?

- Related to gitlab-org/gitlab-ee!581

## Does this MR meet the acceptance criteria?

## Tasks

- [ ]  !5824 Backport changes from EE!581 to CE
    - [x]  Implementation
        - [x]  ::ProtectedBranches::CreateService.new
        - [x]  Can't remove `load_protected_branches_gon_variables`
        - [x]  `has_many` with count enforced
        - [x]  Extract from access levels
        - [x]  project.protected_branches.create(params)
        - [x]  Improve "access_levels.first"
        - [x]  Fix tests
    - [x]  Fix build
    - [x]  Assign to Douwe
    - [ ]  Wait for review/merge

See merge request !5824

# Conflicts:
#	app/controllers/projects/merge_requests_controller.rb

Updated Akismet documentation

Updated Akismet documentation

See merge request !5821

Resolve "Pipelines for merge request"

## What does this MR do?
Adds `Pipelines` tab in merge request view

## What are the relevant issue numbers?
Closes #18681 

## Screenshots (if relevant)
![Screen_Shot_2016-08-16_at_3.22.41_PM](/uploads/c04febab3765b1fac2bf3bbfb9882f9f/Screen_Shot_2016-08-16_at_3.22.41_PM.png)

See merge request !5485

Fix diff comments inverted toggle bug

## What does this MR do?
Explicitly set the comments visibility toggle based on the `active` css class.

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

## Why was this MR needed?
Fixes existing UI bug

## What are the relevant issue numbers?
Closes #20898 

## Screenshots (if relevant)
Before:
![A1ccIDEWsI](/uploads/21175e2008ee4e00225c22afebd873aa/A1ccIDEWsI.gif)

After:
![jHoFp69mAK](/uploads/e85f429d60a4e56d588faec51cd8648a/jHoFp69mAK.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)

See merge request !5818

Fix merge request new view not changing code view rendering style

Correctly respects the code view changing when creating a merge request.

Closes #20808

See merge request !5768

Issue boards

- Issue: #17907
- Issue backend: #20335
- Backend MR: !5548
- Frontend MR: !5554
- Documentation !5713

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

See merge request !5548

Added documentation on adding database indexes

## What does this MR do?

This MR adds a guide on when to add database indexes, how to approach this problem, etc

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

Spelling, grammar, etc

## Why was this MR needed?

Blindly adding indexes can be harmful to the database, and I recently had to remove 48-something unused indexes.

## What are the relevant issue numbers?

#20767

## 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
- [ ] 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 !5771

Revert "Merge branch '19957-write-tests-for-adding-comments-for-different-line-types-in-diff' into 'master'"

This reverts merge request !5417

Add reference to product map.

## What does this MR do?
Mention the product map in the UI Guide and remove a line that says that the GitLab logo and user picture and in the sidebar.

## What are the relevant issue numbers?
19350

- [ ] [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)
Closes #19350

See merge request !5769

Upgrade httpclient gem from 2.7.0.1 to 2.8.2.

Fixes deprecation warnings from Ruby 2.3. Resolves #20950.

Changelog: https://github.com/nahi/httpclient/blob/b51d7a8bb78f71726b08fbda5abfb900d627569f/CHANGELOG.md#changes-in-282

cc: @stanhu 

See merge request !5816

Submit to Akismet Part 1 (Issues)

Related to #5932 #5573 gitlab-com/infrastructure#14

See merge request !5538

Add rspec feature tests for the diff notes feature.

## What are the relevant issue numbers?

Closes #19957.

See merge request !5417

Fixes deprecation warnings from Ruby 2.3.

Changelog: https://github.com/nahi/httpclient/blob/b51d7a8bb78f71726b08fbda5abfb900d627569f/CHANGELOG.md#changes-in-282

This fixes a long running tests due to changed Sidekiq state

## What does this MR do?
Fixes a ordering of tests problem, where GroupsController tests change global state and this affects IrkerService

cc @connorshea 

See merge request !5819

Allow to sort by project size on admin projects page

Fixes #20317

See merge request !5797

Fix attribute inclusion import/export config ignored in some cases

In the `import_export.yml` file we define the inclusion of some of the attributes. For some reason, this isn't working in certain cases - very unfortunate this includes `user`. This has been introduced in 8.10.3.

Related https://gitlab.com/gitlab-org/gitlab-ce/issues/20802

See merge request !1982

Set permissions to admin for importing a project via Import/Export

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/20802

In order to import a project, it is now required to be an admin

Moved from https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5766

See merge request !1983

Add test coverage badge

## What does this MR do?

This MR adds a test coverage badge.

Test coverage badge will be a SVG image you can embed in README.md or on your website that will be created dynamically by GitLab, to show information about how much of the code is being covered by tests. In addition to coverage-regexp feature we currently have, this feature will make it possible to use the coverage data obtained from the build log. We will support both - pipeline coverage, or test coverage for particular job in the pipeline. 

![coverage_badges](/uploads/dfa307339eb58c8138e551b42c0d8756/coverage_badges.png)

![coverage_badge](/uploads/30406e4bdcf979b2900ffe8996728c97/coverage_badge.png)

## What are the relevant issue numbers?

Closes #3714

## Screenshots (if relevant)

## 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)
- [ ] ~~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 !5708

Fix pipeline and build seeds in development environment

## What does this MR do?

When we depend on state machine events in seeds, it is likely that we will break fixtures from time to time because when transition rules change, using events most likely invalidates some objects in seeds

## Why was this MR needed?

Pipeline and build seeds were broken in development environment.

## What are the relevant issue numbers?

Closes #20933

See merge request !5810

When we depend on state machine events in seeds, it is likely that we
will break fixtures from time to time because when transition rules
change, using events most likely invalidates some objects in seeds.