Use rugged to change HEAD

_Originally opened at !2850 by @pmq20._

Needless to invoke gitlab_shell here, which is slow.

See merge request !3705

Issuable can be assigned to author

Closes #9014

The only difference with #9014 is that I thoughed the author should also be
able to assign the issue. If this is unwanted behavior Ill revert it.

/cc @DouweM

See merge request !2765

Delete tags via rugged

Improve the performance by directly using rugged instead of shelling out to a git operation.

See merge request !3748

Remove unused backend methods

Those backend methods are not used anymore since the functionality of them is replaced with rugged.

See merge request !3746

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

Fix required gitlab-shell version in the 8.5 to 8.6 update doc.

Make /profile/keys/new redirects to /profile/keys for back-compat

This addresses https://github.com/gitlabhq/gitlabhq/issues/10138.

See merge request !3717

Do not include award emojis in issue view comment_count

## What does this MR do?

Fixes Issue #14431, changing comment_count on issues index view to not include award emoji comments. While including them is technically correct, it feel nonintuitive in the way comments are presented.

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

No

## Why was this MR needed?

Improves UX of issues view

## What are the relevant issue numbers?

#14431

## Screenshots

### Before
 - ![Issues before](https://monosnap.com/file/cs7lcEkcChXXvAV22y2gh7gBFWCWjj.png)
 - ![MR before](https://monosnap.com/file/qzOawShznyXMKK3Z5cij4SKrHO4jNy.png)
### After
 - ![Issues after](https://monosnap.com/file/IWMedIiGnDnCly7zI5BwNTYQuCS8fH.png)
 - ![MR after](https://monosnap.com/file/mXJu1C2OVo5DGK0XdD67vPZGNPAw4L.png)


See merge request !3610

Report: https://github.com/gitlabhq/gitlabhq/issues/10138Signed-off-by: Rémy Coutable <remy@rymai.me>

Escape the query argument provided to `git grep` by `search_files`

Closes #14963.

See merge request !3633

Under the procedure, I've warned about gitlab-shell version, which should be 2.6.12 (may be some minor revisions introduces that).

Fix datetime format when migrating new notification settings on MySQL

Closes #15264 

See merge request !3733

change "very demand" to "specific demand" in CI runner docs

[ci skip]

See merge request !3726

Copying and pasting doesn't grab line numbers or +/-

Fixes #14176 

See merge request !3687

Add Sentry program context even without a current user



See merge request !3729

Remove deprecated NGINX CI config

[ci skip]

See merge request !3728

Emoji categories fix

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/14020

See merge request !3727

Fixes Issue #14431

Removed references to subscribe-button CSS class

These were being blocked by adblocks

Closes #15043

See merge request !3677

Auto git fsck

Closes https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3232

See merge request !3232

Projects on group page should be sorted by last activity instead of id/created_at
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Fixes #15237 

See merge request !3716

This must be an error as the sentence doesn't make sense otherwise

Fix revoking of authorized OAuth applications

Users were not able to revoke access to authorized OAuth applications. Clicking the "Revoke" button would result in a 404 page, and the application would still be authorized.

Added a spec and also found that the `gon` variables were not being set for this view.

Closes #14370

See merge request !3690

Setup visibility level for project when transfering for a group

fixes #15155 

See merge request !3707

Use rake db:reset instead of db:setup

See merge request !3721