Expire the branch cache after `git gc` runs

Due to a stale NFS cache, it's possible that a branch lookup fails while `git gc` is running and causes missing branches in merge requests.

I'm not totally convinced this is the right solution, but since we and our customers are experiencing this issue quite frequently, I'm taking a stab at it.

Possible workaround for #15392


See merge request !5160

Be explicit on merge request discussion variables

## What does this MR do?

To avoid conditionals and to messing with request.format and accept headers to know in which format we're going to response I've decided to be explicit in when we need the discussion variables

## Why was this MR needed?

Solve a bug https://sentry.gitlap.com/gitlab/staginggitlabcom/issues/8492/

## What are the relevant issue numbers?

Closes #19702 

## Does this MR meet the acceptance criteria?

- [x] [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
- [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 !5204

Style of import project buttons were fixed in the new project page.

## What does this MR do?
I have fixed style of import project buttons in the new project page.

## Are there points in the code the reviewer needs to double check?
I don't think so.

## Why was this MR needed?
Because the buttons area hasn't looked well. Before this, it was scattered.

## What are the relevant issue numbers?
Fixes #19467 

## Screenshots (if relevant)
![Screen_Shot_2016-07-11_at_17.12.11](/uploads/35918f16b1b4d671ad33faf6caf530a2/Screen_Shot_2016-07-11_at_17.12.11.png)
![Screen_Shot_2016-07-11_at_17.11.24](/uploads/3030e1ecb7d109fbf4552987b4bfb242/Screen_Shot_2016-07-11_at_17.11.24.png)
![Screen_Shot_2016-07-11_at_17.11.50](/uploads/eb8ede86c256a2356b0210f3876c0143/Screen_Shot_2016-07-11_at_17.11.50.png)

## Does this MR meet the acceptance criteria?

- [x] [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
- [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 !5183

Due to a stale NFS cache, it's possible that a branch lookup fails
while `git gc` is running and causes missing branches in merge requests.

Possible workaround for #15392

Fix expandable diffs

## What does this MR do?

Fix expandable diffs and the master build.

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

Nope.

## Why was this MR needed?

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4776#note_13003494

Doesn't need a CHANGELOG entry etc.

See merge request !5200

Add rule about adding new header tab to the ui guide

To address cases like https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3749#note_12994215 

See merge request !5188

Update the health_check gem to the latest release

## What does this MR do?
Update the health_check gem to the latest release, which allows us to drop some of our code for overwriting the email check

## Does this MR meet the acceptance criteria?

- [x] [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)

See merge request !5186

api: expose {should,force}_remove_source_branch

## What does this MR do?

Exposes the `should_remove_source_branch` and `force_remove_source_branch` booleans via the API.

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

I don't think so.

## Why was this MR needed?

See the commit message.

## What are the relevant issue numbers?

N/A

## Screenshots (if relevant)

N/A

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

See merge request !5184

Display tooltip for "Copy to Clipboard" button

## What does this MR do?

Add a tooltip to the "Copy to Clipboard" button.

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

Nope.

## Why was this MR needed?

There was no tooltip.

## What are the relevant issue numbers?

fixes #19640, #19682

## Screenshots

(wrong cursor is the fault of my screenshot program)

![after](/uploads/6b89790fa3a32b06b115ef1461cbcd86/after.png)


See merge request !5164

Make "Get started with Builds" Help Page link work properly

`help_page_path('ci/quick_start', 'README')` causes a link to `https://gitlab.com/help/ci%2Fquick_start/README` which in turn breaks every relative link on the page. This remedies the problem.

That said, this is probably a horrible way of fixing this issue, *but* it does work. I can’t find much information on linking this deeply with Rails routes.

If anyone has suggestions as to a better way of handling this, I'll gladly take them. I tried a few different things, but none of them really worked.

Resolves #14872.

cc: @axil @rspeicher @elstamey

See merge request !3561

Optimize cross ref system notes check

## What does this MR do?

This MR optimizes system note visibility checking by memoizing the visible reference count, reducing the overhead of calling `Note#cross_reference_not_visible_for?`.

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

Note that since a cross reference message contains, "Mentioned in XYZ", we EXPECT that there is at least one reference. That's why using the ref count > 0 works. 

## Why was this MR needed?

The previous implementation relied on `Note#cross_reference_not_visible_for?`, which essentially tries to render all the Markdown references in a system note
and only displays the note if the user can see the referring project. But this duplicated the work that Banzai::NotesRenderer was doing already. This shaves about 0.8 s
from the load time from https://gitlab.com/gitlab-com/operations/issues/42.

## What are the relevant issue numbers?

#19273

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [x] [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
  - [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 !5070

Added day name to contributions calendar

## What does this MR do?

Adds the day name text into the contributions calendar tooltip.

## What are the relevant issue numbers?

Closes #19367 

## Screenshots (if relevant)

![Screen_Shot_2016-07-04_at_12.38.52](/uploads/edf6ac3454d479a345aee638875b7713/Screen_Shot_2016-07-04_at_12.38.52.png)

See merge request !5065

have been fully redacted and contain cross-project references.

The previous implementation relied on Note#cross_reference_not_visible_for?,
which essentially tries to render all the Markdown references in a system note
and only displays the note if the user can see the referring project. But this
duplicated the work that Banzai::NotesRenderer was doing already. Instead, for
each note we render, we memoize the number of visible user references and
use it later if it is available.

Improves #19273

Remove pinTo from Flash

## What does this MR do?

- replace `pinTo` of `Flash` by `parent` parameter in constructor
- move positioning of layout containers from CoffeeScript to layout files
- adjust styling of inline flash messages

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

- display of flash messages in general

## Why was this MR needed?

- allow finding and positioning flash message containers within layout files
- allow adding different CSS classes to flash containers within layout files (necessary for fixing #18908)
- allow multiple flash messages to be displayed at different places at the same time
- make inline flash messages look nicer

## What are the relevant issue numbers?

closes #18908, closes part of #18897

## Screenshots

### Inline flash message (before)
![before](/uploads/c5b3cc05140eaeb9d14e481fa506ebbf/before.png)
![before-mobile](/uploads/004b1f2b9510bd97f4f8a7a6e56f17ef/before-mobile.png)

### Inline flash message (after)
![inline-flash-message](/uploads/fe2a23b63623612b696d529e81fa459e/inline-flash-message.png)
![inline-flash-mobile](/uploads/6207604acfebcf7402d77d5638c89ca8/inline-flash-mobile.png)

### Other flash messages (after)

![flash-message-issue](/uploads/d7e12bd0da68cfa333471ed102428cec/flash-message-issue.png)
---
![flash-new-project](/uploads/3465967dba83296068f154f149d26f64/flash-new-project.png)
---
![flash-sign-in](/uploads/4a5b317d5a369034f43343031607a0c2/flash-sign-in.png)
---
![flash-file-comment](/uploads/488a1119374be7e2173c0a590cfd8821/flash-file-comment.png)
---
![flash-fork](/uploads/f41964e8b910801e03eef3d7649e5009/flash-fork.png)
---
![flash-update-profile](/uploads/9fd972d6c6609fbbf86afcd99d343b5f/flash-update-profile.png)
---

### This is possible now

![flashs-everywhere](/uploads/07f425534511fb4ecaa1d7e2a9870787/flashs-everywhere.png)


See merge request !4854

[ci skip]

Clean up coffeescript files imported from GitLab CI

## What does this MR do?

This MR cleans up CoffeeScript files imported from GitLab CI along with a strategy #19159. Some files should have been removed in !1987.

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

While I think the `Build` module should be named as `Build`, not `CiBuild` in the JavaScript namespace, please check if it should.

## Why was this MR needed?

Removing unused coffeescript files reduces time to build JS and so time to transfer even in production. The fewer files, the better, too.

## What are the relevant issue numbers?

Closes #19159

## Screenshots (if relevant)

n/a

## Does this MR meet the acceptance criteria?

- [skipped] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [skipped] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [skipped] API support added
- Tests
  - [skipped] 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 !4925

This is probably a horrible way of fixing this issue, but it does work.
I can’t find much information on linking this deeply with Rails routes.

Resolves #14872.

Fix problems with events under notes importing GitLab projects

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/19588

See merge request !5154

Workflows which use a bot to merge should remove branches if requested.
Expose the flag so that bots can request know this.

Correctly shows close button on merge requests

Closes #19403 

See merge request !5036

Allow SentNotification#position to be set as string or hash

Fixes https://sentry.gitlap.com/gitlab/staginggitlabcom/issues/8491/

See merge request !5189

Single file diffs

Closes #14103. Related (not part of this MR): #19553.

This adds a `diff_for_path` action to each place we render diffs (commit, compare, new MR, existing MR) which renders the diff for a single path. The action is always available with the same params as the 'parent' action, to make it simpler to generate the URIs.

If a diff is bigger than 10 KB, it will be collapsed by default and have a data attribute added. You can then click the message or the filename to expand that diff. For expanded files, you can collapse and expand them, but they won't make any AJAX requests.

![Expand_and_collapse_diffs](/uploads/a4072029085082b85c47006f67ac531c/Expand_and_collapse_diffs.gif)

See merge request !4990

entities: remove :description from MergeRequest

## What does this MR do?

Removes a duplicate `description` key from API JSON objects.

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

No.

## Why was this MR needed?

`description` is already exported via `ProjectEntity` and doesn't need to be listed in `MergeRequest` as well.

## What are the relevant issue numbers?

N/A

## Screenshots (if relevant)

N/A

## 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)

See merge request !5099

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

This allows us to drop our disable email config override

Use Gitlab-Workhorse-Send-Data to send entry

## What does this MR do?

Use Gitlab-Workhorse-Send-Data to send entry:

Closes #19224, Closes #19128

Also requires this MR to work:
https://gitlab.com/gitlab-org/gitlab-workhorse/merge_requests/53

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

Do we have a test for this?

## Why was this MR needed?

This way gitlab-workhorse does not have to call any API.

See merge request !5094