Add Mock CI service/integration

See merge request !9250

Fixed alignment of RSS button on activity pages

Closes #28572

See merge request !9478

Improved the diff comment button UX

Closes #27543

See merge request !9448

Pipelines tables UI improvements

Closes #28383, #26611, #21788, #27048, and #27828

See merge request !9442

Add runner version to /admin/runners view

See merge request !8733

Make nested groups deletion synchronous to avoid potential race

See merge request !9288

fix ERR_CONTENT_LENGTH_MISMATCH on task checkboxes

See merge request !8567

Improves backoff algo with maxInterval between requests

See merge request !9548

Update Registry administration doc - external registry

Closes omnibus-gitlab#1361

See merge request !8497

Backport EE http status codes new file to CE

Closes #28721

See merge request !9549

* master: (196 commits)
  Add quotes to coverage pattern
  Update CHANGELOG.md
  Bump omniauth to 1.4.2
  Bump Hashie to 3.5.5 to eliminate warning noise
  use single backticks for inline code
  Add performance query regression fix for !9088 affecting #27267
  Fix spec
  API: Return 400 for all validation erros in the mebers API
  Adds confirmation for cancel button
  Add newline
  Corrected indentation on the template string
  Adds backoff algo from EE to CE
  We don't need these checks anymore
  Raise error when no content is provided
  Address review
  Update API v3 in line with v4
  Fix new offenses
  Fix spec
  Fix specs
  Rename commit_file, commit_dir and remove_file and update specs
  ...

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

Add the username of the current user to the HTTP(S) clone URL

Closes #1937

See merge request !9347

Update manage_large_binaries_with_git_lfs.md

See merge request !9412

Query performance regression fix affecting "Dashboard::ProjectsController#index.atom"

Closes #27267

See merge request !9526

API: Return 400 for all validation erros in the mebers API

See merge request !9523

Add Runner registration/deletion API

See merge request !9246

Bump Hashie to 3.5.5 and omniauth to 1.4.2 to eliminate warning noise

Closes #28595

See merge request !9534

Fixed hll overriding is-over class

It now shows the line will be commenting on my highlight the line number cells with a lighter color. The button has also been made smaller, it was previously way over the top & took over a lot more space than it should of done

Closes #27543

Add quotes to coverage pattern

See merge request !9545

Adds backoff algo from EE to CE

See merge request !9517

Update Vue to v2.1

See merge request !9386

Add clearer placeholders and channel definition for Mattermost and Slack notifications services

See merge request !9139

[ci skip]

Closes #28595

Make Git history follow renames again by performing the --skip in Ruby

Closes #23062

See merge request !9314

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

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

Update users.md

See merge request !9475