Fix Error 500 when creating Wiki pages with hyphens or spaces

- Closes gitlab-com/support-forum#874
- Closes #20209 

See merge request !5444

1. So we can build the markdown preview URL for it.

2. We can't skip the slug in this case, because the slug is used to
construct relative markdown URLs.

3. Add rspec feature tests to cover creating wiki pages with
   spaces/hyphens in the name.

4. Add rspec feature tests for markdown preview URL rewriting, which was
   only covered by unit tests up to this point.

ES6ify all the things!



See merge request !5464

Revert "Merge branch '17073-tagscontroller-index-is-terrible-response-time-goes-up-to-5-…"

## What does this MR do?

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

## Why was this MR needed?

## What are the relevant issue numbers?

## Screenshots (if relevant)

## 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 !5461

This reverts merge request !5375

Closes gitlab-com/support-forum#874

Add links to the real markdown.md file for all GFM examples

## What does this MR do?

Add links to the real markdown.md file for all GFM examples since they will not render correctly on docs.gitlab.com.

We already have a note https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5440, but better be explicit.

See merge request !5458

Fix bug where replies to commit notes displayed in the MR discussion tab wouldn'…

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/20157

See merge request !5446

Add gitlab-workhorse version to admin dashboard

## What does this MR do?
Add gitlab-workhorse version to admin dashboard.

## What are the relevant issue numbers?
Closes #15418 

## Screenshot
![Zrzut_ekranu_2016-07-20_o_23.20.55](/uploads/ba6761e2145d903ac87bc7198bc8b182/Zrzut_ekranu_2016-07-20_o_23.20.55.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] Add test - show Gitlab Workhorse version on Admin Dashboard
  - [x] All builds are passing
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)

cc @ubudzisz @yorickpeterse @grzesiek [@chastell](https://github.com/chastell) [@tomash](https://github.com/tomash)

See merge request !5321

Fix bug where replies to commit notes displayed in the MR discussion tab wouldn't show up on the commit page

Improve project rename log messages for better debugging

This should help diagnose issues such as #20178.

See merge request !5450

Add light border to rounded avatars

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/20128

To make it clear that avatar is cropped by border radius

cc @hazelyang 

See merge request !5429

Helping to diagnose #20178

Test for showing GitLab Workhorse version on Admin Dashboard

Refactoring

Add note to say GFM doesn't work on documentation website



See merge request !5440

Fix missing repo_ref param

Closes #19444

See merge request !5435

Load project invited groups and members eagerly in ProjectTeam#fetch_members

## What does this MR do?
Load project invited groups and members eagerly in `ProjectTeam#fetch_members`, reducing number of queries to DB.

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

## Why was this MR needed?
`ProjectTeam#fetch_members` is part of the code path of `Participable#raw_participants`, so it should improve its performance a bit.

## 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 !5436

Gracefully handle case when keep-around references are corrupted or exist already

We were seeing a number of error messages when attempting to create a keep-around ref:
    
1. Failed to create locked file `refs/keep-around/XYZ`: File exists
2. Failed to write reference `refs/keep-around/XYZ`: a reference with that name already exists.
    
I'm not sure how these happen, but I suspect when multiple workers attempt to write the same file we may have an issue. The force parameter should help ensure the file gets created,
as well as the rescues to prevent 500 Errors.
    
Rugged/libgit2 unfortunately does not allow you to delete or re-create a reference that has been corrupted, even with the force parameter. A truncated reference will stay that way until manual intervention.
    
Closes #20109


See merge request !5430

Add detailed info on storage path mountpoints

Users that run GitLab from source should be extra careful when using the
multiple repository storage feature. Make sure there is a detailed explanation
why this happens and how to overcome it.

See merge request !5437

[ci skip]

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

We were seeing a number of error messages when attempting to create a keep-around ref:

1. Failed to create locked file `refs/keep-around/XYZ`: File exists
2. Failed to write reference `refs/keep-around/XYZ`: a reference with that name already exists.

I'm not sure how these happen, but I suspect when multiple workers attempt to write the same
file we may have an issue. The force parameter should help ensure the file gets created,
as well as the rescues to prevent 500 Errors.

Rugged/libgit2 unfortunately do not allow you to delete or re-create a reference that has
been corrupted, even with the force parameter.

Closes #20109

Make Notify specs more robust by setting up assignee names

Closes #20121.

See merge request !5427

Refactor repository storages documentation

Use detailed information on using the multiple repository storage feature

See merge request !5428

[ci skip]

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

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

Merge branch '20107-update-documentation-according-to-the-new-multiple-repository-storage-paths-feature' into 'master'

Update documentation according to the new multiple git mount points feature

Closes #20107

See merge request !5411

Refactor Slack service documentation



See merge request !5421

[ci skip]

Move admin application settings to own path

Move existing documentation to its own `user/admin_area/settings` path.

See merge request !5420

Refactor protected branches documentation

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/19832

See merge request !5419