Avoid data-integrity issue when cleaning up repository archive cache

## What does this MR do?
Sets the default value for `repository_downloads_path` if someone has it configured incorrectly, and it points to the path where repositories are stored. It's also replace invocation of `find` with Ruby code that matches old cached files in a better, and safe way to avoid data-integrity issues.

## Why was this MR needed?
The `repository_downloads_path` is used by the `RepositoryArchiveCacheWorker` to remove outdated repository archives, if it points to the wrong directory can cause some data-integrity issue.

## What are the relevant issue numbers?
Closes #14222

See merge request !5285

Reduce min width of pipeline table

## What does this MR do?
Reduce min width of pipeline table

## Why was this MR needed?
The current min-width is based on the heavily populated pipelines page main table. This pipeline table doesn't have nearly as much information so can be collapsed down a lot further

![table](/uploads/895d2fb2f01383a841f973e918199f55/table.gif)   
cc @markpundsack 


See merge request !5409

Retrieve rendered HTML from cache in one request

## What does this MR do?
It consolidates requests made to cache store to check for cached HTML of multiple Markdown texts (for reference extracting purposes) into one request.

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

## Why was this MR needed?
To improve the performance of `Participable#raw_participants`

## What are the relevant issue numbers?
#19985 

## 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
- ~~[ ] [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 !5406

Refactor Issues::BulkUpdateService spec

- Create fewer Issue objects; 2 is as good as 5 for these cases. This
  gives us a nice little speed improvement.
- Don't `describe` Symbols.
- Simplify object creation.
- Lessen "mystery guest" antipattern

See merge request !5380

See #19985

Add Discussion model to represent MR/diff discussion

Related to https://gitlab.com/gitlab-org/gitlab-ce/issues/10325.

See merge request !5376

UI bug fixes

Closes #20074   
Closes #20094 

Regression UI bug fixes
* Fix broken status icon on project page
* Center tooltip on empty state in pipeline
* Reduce max-width of commit title in pipeline so more fits in table
* Fixes firefox rendering (icons getting cut off)
* Fixes Safari rendering of SHA icon

See merge request !5383

Bump vmstat version to fix issues reporting on FreeBSD

Minor changes from 2.1.0 to 2.1.1:

https://github.com/threez/ruby-vmstat/commits/master

See merge request !5405

Don't drop in DropAndReaddHasExternalWikiInProjects

## What does this MR do?

This MR fixes the migration in question so it doesn't first drop and then re-add a column.

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

Not really.

## Why was this MR needed?

The old migration could lead to application errors as the column would temporarily not exist between the drop column and add column statements.

## What are the relevant issue numbers?

https://gitlab.com/gitlab-com/infrastructure/issues/239

## 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] 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 !5402

Add allow_failure CI documentation

## What does this MR do?

Adds documentation for the `allow_failure` keyword for the CI.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/17669

See merge request !5398

Dropping a column and then re-adding it can lead to the application
throwing errors as the column may temporarily not exist. To work around
this we'll reset the various project rows in batches _without_ removing
any columns.

Don't use `params[:id]` while building `markdown_preview_path`.

- Closes #20079

See merge request !5400

Replace invocation of `find` with Ruby code that matches old cached
files in a better, and safe way to avoid data-integrity issues.

1. Instead, use `@page.title`, since it's always guaranteed to be around
   in a wiki.

2. `params[:id]` is _not_ always guaranteed to be around - if a page is
    created with errors, `render :edit` is called, and `params[:id]` is
    `nil`.

3. More context: https://gitlab.com/gitlab-org/gitlab-ce/issues/20079#note_13223240

Fix migration to make it fast

## What does this MR do?

Changing the migration introduced in !5387 so that it's fast. The idea is that the content of the `projects.has_external_wiki` is currently wrong, so we can just drop and recreate the column.

## Does this MR meet the acceptance criteria?

- [x] No CHANGELOG needed
- Tests
  - [ ] 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 !5394

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

Cast duration to integer in `TimeHelper#time_interval_in_words`

Fixes #20055.

- [x] No CHANGELOG since it fixes a regression introduced in RC12.
- 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)
- [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 !5391

Fix emails on push for new and deleted branches

## What does this MR do?

Fix EmailsOnPushWorker when the push is either a new branch or a deleted branch.

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

Don't think so.

## Why was this MR needed? / What are the relevant issue numbers?

Closes #20061.

## Does this MR meet the acceptance criteria?

- ~~[CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added~~ (regression)
- ~~[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
  - [ ] 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 !5390

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

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

Show tooltip on GitLab export link in new project page

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/19993

When the project path/name is not filled, we should show a tooltip in the `GitLab export` link, plus a flash message if the user still tries to click on it.

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry 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)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5363