MR: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9250/

See https://gitlab.com/madlittlemods/gl-mock-ci-service

Conflicts:
	lib/api/services.rb

Port of dm-fix-web-edit-new-lines to EE

See merge request !1248

remove Turbolinks from lockfile.js, do page refresh instead

See merge request !1299

Enable the RSpec/BeEql cop

See merge request !1295

Deleting a user shouldn't delete associated issues.

See merge request !862

Remove ProjectGitHook API

Closes #1791

See merge request !1301

Document how to use filter-branch to reduce the repo file size

Closes #1270

See merge request !914

[ci skip]

CE upstream: Thursday

See merge request !1293

Fit GitAccess specs

See merge request !1297

Fix GitAccess specs

Closes #28620

See merge request !9479

Resolve "Test compiling frontend assets for production in CI"

Closes #28450

See merge request !9396

on branch deletion show loading icon and disabled the button

See merge request !6761

- Add a `destroy_user` ability. This didn't exist before, and was implicit in
  other abilities (only admins could access the admin area, so only they could
  destroy all users; a user can only access their own account page, and so can
  destroy only themselves).

- Grant this ability to admins, and when the current user is trying to destroy
  themselves. Disallow destroying ghost users in all cases.

- Modify the `Users::DestroyService` to check this ability. Also check it in
  views to decide whether or not to show the "Delete User" button.

- Add a short summary of the Ghost User to the bio.

- Have `Uniquify` take a block instead of a Proc/function. This is more
  idiomatic than passing around a function in Ruby.

- Block a user before moving their issues to the ghost user. This avoids a data
  race where an issue is created after the issues are migrated to the ghost user,
  and before the destroy takes place.

- No need to migrate issues (to the ghost user) in a transaction, because
  we're using `update_all`

- Other minor changes

The default (false) is not strictly required, and this lets us avoid a
potentially expensive migration

1. Refactoring and specs in the `Uniquify` class.

2. Don't use the `AdvisoryLocking` class. Similar functionality is
provided (backed by Redis) in the `ExclusiveLease` class.

Rather than using a separate `ghost` state. This lets us have the benefits of
both ghost and blocked users (ghost: true, state: blocked) without having to
rewrite a number of queries to include cases for `state: ghost`.

1. Use an advisory lock to guarantee the absence of concurrency in `User.ghost`,
to prevent data races from creating more than one ghost, or preventing the
creation of ghost users by causing validation errors.

2. Use `update_all` instead of updating issues one-by-one.

1. Create a `Uniquify` class, which generalizes the process of generating unique
   strings, by accepting a function that defines what "uniqueness" means in a
   given context.

2. WIP: Make sure tests for `Namespace` pass, add more if necessary.

3. WIP: Add tests for `Uniquify`