Bump Git version requirement to 2.8.4

Following gitlab-org/omnibus-gitlab!1108, the install doc and README should be updated too.

See merge request !7878

Bump gitlab-shell version to 4.0.3

See merge request !7953

Move admin hooks spinach to RSpec

https://gitlab.com/gitlab-org/gitlab-ce/issues/23036

See merge request !7942

Move admin logs spinach test to RSpec

https://gitlab.com/gitlab-org/gitlab-ce/issues/23036

See merge request !7945

UX Guide - add initial animation guidance

Adding guidance to our UX Guide around animation. This is to help us implement #24831 and add polished, consistent animation throughout GitLab.

See merge request !7780

Use :maximum instead of :within for length validators with a 0..N range

Closes #25209

See merge request !7894

Update php.md - /.dockerinit was removed in v1.11 so the test always results in …

See merge request !7882

Add excoveralls in list of coverage examples

See merge request !7906

Update custom_hooks.md for chained hooks support

See merge request !6721

Fix 404 error when visit group label edit page

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/25158

See merge request !7957

Remove caching of Repository#has_visible_content?

This MR removes the caching of `Repository#has_visible_content?`. The cache for this method is no longer necessary and this should solve the problem described in https://gitlab.com/gitlab-org/gitlab-ce/issues/25278.

See merge request !7947

A simpler implementation of finding a merge request

## What does this MR do?

This cleans up some code in the issues API as discussed in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7180#note_19501743

The helper method `merge_request_for_resolving_discussions` was no longer needed as it was only used once. That made it possible to simplify the implementation.

## Does this MR meet the acceptance criteria?

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

!7180

See merge request !7955

Remove more pages css

* Moves award emojis to `/framework`
* Moves generic image styles to `/framework`
* Removes `confirmation.scss`

See merge request !7952

Remove dashboard.scss

See merge request !7960

# Conflicts:
#   app/assets/stylesheets/framework.scss

Remove tags.scss

Remove `tags.scss`

See merge request !7935

Remove admin.scss

Removes admin-specific CSS

See merge request !7932

https://gitlab.com/gitlab-org/gitlab-shell/merge_requests/93

https://gitlab.com/gitlab-org/gitlab-ce/issues/23036

https://gitlab.com/gitlab-org/gitlab-ce/issues/23036

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

Following a discussion in !7180

Encourage bug reporters to mention if they use GitLab.com [ci skip]

See merge request !7954

Explain "js: true" in "deleted_source_branch_spec.rb"

See merge request !7949

Create an issue for all unresolved discussions in an MR

See merge request !7180

Fix Archived project merge requests add to group's Merge Requests

Closes #24733

See merge request !7790

Guests can read builds if those are public

See merge request !6842

Refine CI Statuses

## What does this MR do?

This MR introduces classes for each relevant CI status.

## What are the relevant issue numbers?

Closes #24273

See merge request !7889

Use `--extended-regexp` in lint-doc for compatibility with Darwin grep

Now it should work on all platforms.

See merge request !7943

This method already uses the cached method Repository#branch_count so
there's no point in also caching has_visible_content?.

Fixes gitlab-org/gitlab-ce#25278