Replace MR access checks with use of MergeRequestsFinder

Split from !2024 to partially solve https://gitlab.com/gitlab-org/gitlab-ce/issues/23867

⚠ - Potentially untested
💣 - No test coverage
🚥 - Test coverage of some sort exists (a test failed when error raised)
🚦 - Test coverage of return value (a test failed when nil used)
✅ - Permissions check tested

- [x] 💣  app/finders/notes_finder.rb:17
- [x] ⚠  app/views/layouts/nav/_project.html.haml:80 [`.count`]
- [x] 💣  app/controllers/concerns/creates_commit.rb:84
- [x] 🚥  app/controllers/projects/commits_controller.rb:24
- [x] 🚥  app/controllers/projects/compare_controller.rb:56
- [x] 🚦  app/controllers/projects/discussions_controller.rb:29
- [x] ✅  app/controllers/projects/todos_controller.rb:27
- [x] 🚦  app/models/commit.rb:268
- [x] ✅ lib/gitlab/search_results.rb:71

- [x] https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/2024/diffs#d1c10892daedb4d4dd3d4b12b6d071091eea83df_267_266 Memoize ` merged_merge_request(current_user)`
- [x] https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/2024/diffs#d1c10892daedb4d4dd3d4b12b6d071091eea83df_248_247 Expected side effect for `merged_merge_request!`, consider `skip_authorization: true`.
- [x] https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/2024/diffs#d1c10892daedb4d4dd3d4b12b6d071091eea83df_269_269 Scary use  of unchecked `merged_merge_request?`

See merge request !2033

Don't accidentally mark unsafe diff lines as HTML safe

Fixes potential XSS issue when a legacy diff note is created on a merge
request whose diff contained HTML

See https://gitlab.com/gitlab-org/gitlab-ce/issues/25249

See merge request !2040

Add authentication_token to filter_parameters list

See merge request !2041

Destroy a user session when they delete their own account via browser

This patch destroys a user's session when they delete their own account
using a browser. A new session is created as they are redirected to the
sign_in page.

Issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/25015

See merge request !2042

Fix JS error when reseting new issue template

Fixes JS error when trying to reset template when no template has been set.

See merge request !7978

Fade out should be white instead of gray

Currently, you can see the hard edge of the fade out because it's a light shade of gray rather than white.   
Before:   
![Screen_Shot_2016-12-07_at_12.36.10_PM](/uploads/c8fd2c6ba1742d1260614fd4c9cb29c9/Screen_Shot_2016-12-07_at_12.36.10_PM.png)
After:   
![Screen_Shot_2016-12-07_at_12.35.53_PM](/uploads/52b51e4a825658a0c440e0f1fb86a31c/Screen_Shot_2016-12-07_at_12.35.53_PM.png)
cc @nmrony

See merge request !7979

Various small emoji positioning adjustments

## What does this MR do?
It changes various emoticon related css rules with very small minor tweaks of 1 or 2 px

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

## Why was this MR needed?
aesthetics

## Screenshots (if relevant)
-


## Does this MR meet the acceptance criteria?

- [X] [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?
none

See merge request !7993

Fixed timeago re-rendering every element

## What does this MR do?

Fixes an issue when new notes are added timeago will be initialised for every timeago element on the page again and therefore adding more timeouts.

See merge request !7969

Refine pipeline stages

## What does this MR do?

Introduces a concept of `Ci::Stage` to make it easier to have detailed statuses.

## Why was this MR needed?

This is needed to simplify the handling of `Ci::Statuses` and make the `Stage` actual concept in code:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7889

See merge request !7927

Remove wrong '.builds-feature' class from the MR settings fieldset

Closes #25171

See merge request !7930

Closes #24982

See merge request !7837

Don't whitelist events for all filter

Closes #24826

See merge request !7673

Remove unnecessary target branch link from MR page in case of deleted target branch

Fixes #24507

See merge request !7916

Shows group members in the project members list

Closes #24122

See merge request !7899

Update factory_girl_rails to 4.7.0

Changes: https://github.com/thoughtbot/factory_girl/blob/master/NEWS

See merge request !7986

Enable display of admonition icons in Asciidoc.

## What does this MR do?

Enables admonition icons to display in rendered asciidoc documents.

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

## Why was this MR needed?

Gitlab support of asciidoc needs a lot of improvements to make it useful in enterprise settings.

## Screenshots (if relevant)

![Screenshot_20161129_132250](/uploads/d280336000eb8b445d07d9bb2a2ed639/Screenshot_20161129_132250.png)

## Does this MR meet the acceptance criteria?

- [x] [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
- [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 !7812

Correct previous stable branch used in 8.14 to 8.15 update guide

[ci skip]

See merge request !7984

Allow public access to some Tag API endpoints

Continuation of #4269.

See merge request !7896

Reenables /user API request to return private-token if user is admin and requested with sudo

## What does this MR do?

Reenables the API /users to return `private-token` when sudo is either a parameter or passed as a header and the user is admin.

## Screenshots (if relevant)

Without **sudo**:

![Screen_Shot_2016-11-21_at_11.44.49](/uploads/ebecf95dbadaf4a159b80c61c75771d9/Screen_Shot_2016-11-21_at_11.44.49.png)

With **sudo**:
![Screen_Shot_2016-11-21_at_11.45.52](/uploads/f25f9ddffcf2b921e9694e5a250191d3/Screen_Shot_2016-11-21_at_11.45.52.png)

## 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
  - [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?


Closes #24537

See merge request !7615

[ci skip]

When rendering Asciidoc documents this merge request enables the diplay of
admonition blocks using font icons. This improves the looks of Asciidoc redered
files.

This uses the font-awesome fonts already present in Gitlab so no large
dependencies are required for this to work.

add link_to_if helper on target_branch link on Merge Request show page for case of deleted target branch

add spec on #24507 bug description

add changelog entry

fix changelog

remove unnecessary js:true from specs

change spec title

add test for link to target branch before deletions

renamed spec about state of target branch link before and after deletion

some fixes into spec

Update outdated visible content spec descriptions

This fixes some spec descriptions that were not fixed in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7947.

See merge request !7971

Fix Backup::Manager#remove_old

Closes #25399

See merge request !7972

Fix typos in API doc examples

## What does this MR do?

Fixes a typo in the API docs. The `curl` examples in [build_triggers.md](doc/api/build_triggers.md) and [build_variables.md](doc/api/build_variables.md) all have a typo in the auth header. They all say `PRIVATE_TOKEN` when it should be `PRIVATE-TOKEN`.

## What are the relevant issue numbers?
Fixes #24565

See merge request !7514

Run builds with runners with tags gitlab-org and 2gb

## What does this MR do?

Added `gitlab-org` and `2gb` tags for jobs in `.gitlab-ci.yml`. So builds will be picked up by `gitlab-shared-runners-manager-X.gitlab.com runners`

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

Only `.gitlab-ci.yml`

## Why was this MR needed?

https://gitlab.com/gitlab-com/infrastructure/issues/714

## Screenshots (if relevant)


## 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?

https://gitlab.com/gitlab-com/infrastructure/issues/714

See merge request !7757

Grapify the issues API

Related to #22928

See merge request !7968

Update GLU index for new report, broken links + typos

## What does this MR do?
Update text on GLU documentation for spelling and new State of DevOps book. 

/cc @axil

See merge request !7962

After this change the sign-in-success flash message will not be shown

refactor: set flash message to be nil while signing in

test: changed tests to reflect removal of sign-in message

refactor: adding signed_in message back

See Merge Request !7837

issue#24982

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