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

Show pipeline status from branch and commit than only commit

Closes #23615

See merge request !7034
Signed-off-by: Rémy Coutable <remy@rymai.me>

Resolve "Introduce round-robin project creation to spread load over multiple shards"

Allow multiple shards to be enabled in the admin settings page, balancing project creation across all enabled shards.

* `f.select ..., multiple: true` isn't the most beautiful UI in the world, but switching to `collection_check_boxes` (or a facsimile thereof) isn't trivial
* Should `pick_repository_storage` be a method of `ApplicationSetting`, or `Project`? It's going to accrete logic over time so perhaps it should be its own class already?
* This is written to avoid the need for a database migration, so it is`serialize :repository_storage` without `, Array`. This is tested, but alternatives include:
  * Add a database migration
  * Write a custom Coder that will accept a String or Array in `load` and always `dump an Array.

Closes #24059

See merge request !7273
Signed-off-by: Rémy Coutable <remy@rymai.me>

See merge request !7014
Signed-off-by: Rémy Coutable <remy@rymai.me>

Fix lightweight tags not processed correctly by GitTagPushService

Closes #22271

See merge request !6532
Signed-off-by: Rémy Coutable <remy@rymai.me>

Fixes #24102

See merge request !7267

Only skip group when it's actually a group in the "Share with group" select

Fixes #23961

See merge request !7262

Fix project features default values

closes #23242

See merge request !7181
Signed-off-by: Rémy Coutable <remy@rymai.me>

Fix builds tab visibility

closes #23951

See merge request !7178
Signed-off-by: Rémy Coutable <remy@rymai.me>

Optimize group labels page

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/23684

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/1148

See merge request !7123
Signed-off-by: Rémy Coutable <remy@rymai.me>

Allow owners to fetch source code in CI builds

Due to different way of handling owners of a project, they were not allowed to fetch CI sources for project.

This adds a separate code path for handling owners, that are not admins.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/23437

See merge request !6943
Signed-off-by: Rémy Coutable <remy@rymai.me>

Respect project visibility settings in the contributions calendar

This MR fixes a number of bugs relating to access controls and date selection of events for the contributions calendar

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/23403

See merge request !2019

Ensure external users are not able to clone disabled repositories.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/23788

See merge request !2017

disable markdown in comments when referencing disabled features

fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/23548

This MR prevents the following references when tool is disabled:

- issues
- snippets
- commits - when repo is disabled
- commit range - when repo is disabled
- milestones

This MR does not prevent references to repository files, since they are just markdown links and don't leak
information.

See merge request !2011
Signed-off-by: Rémy Coutable <remy@rymai.me>

Honour issue and merge request visibility in their respective finders

This MR fixes a security issue with the IssuesFinder and MergeRequestFinder where they would return items the user did not have permission to see. This was most visible on the issue and merge requests page for a group containing projects that had set their issues or merge requests to "private".

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/22481

See merge request !2000
Signed-off-by: Rémy Coutable <remy@rymai.me>

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

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

Merge branch '23872-members-of-group-that-has-project-access-getting-404-on-accessing-a-project-issue' into 'master'

Fix project member access for group links

Closes #23872.

See merge request !7144
Signed-off-by: Rémy Coutable <remy@rymai.me>

Increase z index on fixed mr tabs

Before:
<img src="/uploads/e890a4f185af87b66251d744fbe840d5/Screen_Shot_2016-10-26_at_11.58.45_AM.png" width="400px">

After:
<img src="/uploads/0bbf72888f6a47bd3027ee7dfff542da/Screen_Shot_2016-10-26_at_11.58.28_AM.png" width="400px">
Closes #23866

See merge request !7124
Signed-off-by: Rémy Coutable <remy@rymai.me>

Pass user instance to Labels::FindOrCreateService or skip_authorization: true

It fixes a bug described in #23694 when `project.owner` was passed to `Labels::FindOrCreateService`. `Labels::FindOrCreateService` expected a user instance and `project.owner` may return a group as well. This MR makes sure that we either pass a user instance or `skip_authorization: true`.

Fixes #23694

See merge request !7093
Signed-off-by: Rémy Coutable <remy@rymai.me>

Resolve "Lacking padding on syntax highlight blocks in diff comments"

Enforces horizontal padding on highlight block.

There was no horizontal padding on diff comment highlight blocks.

Closes #23661

See merge request !7062
Signed-off-by: Rémy Coutable <remy@rymai.me>

Fix refs dropdown selection with special characters

Remove unneeded encode from the project-refs-dropdown renderRow method.

Closes #21248

See merge request !7061
Signed-off-by: Rémy Coutable <remy@rymai.me>

Modify GitHub importer to be retryable

Closes #23533

See merge request !7003
Signed-off-by: Rémy Coutable <remy@rymai.me>

Fix couple of GitHub importing bugs

Fix a bug in GH comment importing and label applying for imported MRs.

See merge request !7139
Signed-off-by: Rémy Coutable <remy@rymai.me>

Only remove right connector of first build of last stage

Closes #23849

See merge request !7179
Signed-off-by: Rémy Coutable <remy@rymai.me>

Use Hash rocket syntax to fix cycle analytics under Ruby 2.1

Refers to #23510

See merge request !6977
Signed-off-by: Rémy Coutable <remy@rymai.me>

Fix encoding issues on pipeline commits

## What does this MR do?
#### What does this MR do?
Sets `escape: false` on `truncate` method to fix commit message on pipelines page

#### Screenshots (if relevant)
Before:   
![Screen_Shot_2016-10-12_at_8.53.10_AM](/uploads/5e26e98a272139fe2264c315d579178f/Screen_Shot_2016-10-12_at_8.53.10_AM.png)
After:   
![Screen_Shot_2016-10-12_at_8.52.49_AM](/uploads/58c6c69f2ba735fdcd5a0b6922b56aa7/Screen_Shot_2016-10-12_at_8.52.49_AM.png)

#### What are the relevant issue numbers?
Closes #23258

See merge request !6832

API: Fix booleans not recognized as such when using the `to_boolean` helper

Fixes #22831
Fixes #23890

See merge request !7149

Fix and improve `Sortable.highest_label_priority`

Closes #23928

See merge request !7165

Fixed sticky MR tabs positioning when sidebar is pinned

## What does this MR do?

The sticky MR tabs where positioned underneath the pinned sidebar. This fixes that by accounting for the size of the pinned nav.

## Screenshots (if relevant)

![Screen_Shot_2016-10-28_at_09.37.18](/uploads/0d23f2bb0e02d698c012c22c8653afd7/Screen_Shot_2016-10-28_at_09.37.18.png)

## What are the relevant issue numbers?

Closes #23926

See merge request !7167

Fix CHANGELOG for GH import fixes

See merge request !7173

Merge branch 'ee-1159-allow-permission-check-bypass-in-approve-access-request-service' into 'master'

Allow Members::ApproveAccessRequestService to accept a new `:force` option

## What does this MR do?

See the commit message.

This is a backport of the EE fix for https://gitlab.com/gitlab-org/gitlab-ee/issues/1159: gitlab-org/gitlab-ee!830

See merge request !7168

Update gitlab-shell version to 3.6.6

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/23659

See merge request !7118

[ci skip]

Fix events order in users/:id/events endpoint

Order of events in contributions API is currently being lost, though docs are saying:

> Get the contribution events for the specified user, sorted **from newest to oldest**.

Order becomes different after `.merge(ProjectsFinder.new.execute(current_user))` call, so I moved ordering below this line.

This MR also removes extra `.page(params[:page])` call in the method chain, since [`paginate(events)` already does it](https://gitlab.com/airat/gitlab-ce/blob/master/lib/api/helpers.rb#L112).

See merge request !7039
Signed-off-by: Rémy Coutable <remy@rymai.me>