Move all rugged operation for ff_merge inside Gitlab::Git

Closes gitaly#683

See merge request gitlab-org/gitlab-ce!15011

Add case insensitive branches search

Closes #35199

See merge request gitlab-org/gitlab-ce!14995

Resolve "Remove overzealous tooltips in projects page tabs"

Closes #39419

See merge request gitlab-org/gitlab-ce!15017

Remove filter icon from search bar

Closes #32318

See merge request gitlab-org/gitlab-ce!14966

We also delete some unused code related to the aforementioned feature.

Remove superfluous namespace from cluster settings

See merge request gitlab-org/gitlab-ce!14987

Support `Gitaly::User`'s gl_username field

See merge request gitlab-org/gitlab-ce!15016

Don't rename groups/projects that aren't reserved anymore

Closes #39387

See merge request gitlab-org/gitlab-ce!15029

In https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/12932 we
freed up some names. But we were still renaming them.

Memoize GitLab logger to reduce open file descriptors

Closes gitlab-ee#3664

See merge request gitlab-org/gitlab-ce!15007

Suggest to rename the remote for existing repositories

See merge request gitlab-org/gitlab-ce!14970

We see that in gitlab-org/gitlab-ee#3664 that if we log a lot of
data in Sidekiq workers, the number of open file descriptors
reaches over 1000. To avoid this, we can memoize the logger per
thread via RequestStore.

Closes gitlab-org/gitlab-ee#3664

Update groups API documentation

Closes #38922

See merge request gitlab-org/gitlab-ce!15024

Fix the writing of invalid environment refs

Closes #39182

See merge request gitlab-org/gitlab-ce!14993

Resolve "Pages API"

Closes #23000

See merge request gitlab-org/gitlab-ce!13917

Circuitbreaker backoff and retries

Closes #37383 and #38231

See merge request gitlab-org/gitlab-ce!14933

Add new files & directories in the multi-file editor

Closes #38614

See merge request gitlab-org/gitlab-ce!14839

Hides pipeline duration in commit box when it is zero (nil)

Closes #32788

See merge request gitlab-org/gitlab-ce!14979

Clean up `new-sidebar`

See merge request gitlab-org/gitlab-ce!14978

Fix code review discussion action buttons

Closes #38891

See merge request gitlab-org/gitlab-ce!14801

Fix performance of sticky.js

Closes #39332

See merge request gitlab-org/gitlab-ce!14976

Remove Sherlock usage from the performance bar

Closes #39351

See merge request gitlab-org/gitlab-ce!15000

Changing the smallest of typos

See merge request gitlab-org/gitlab-ce!15022

Use the new buttons for creating groups and projects in QA tests

Closes #39349

See merge request gitlab-org/gitlab-ce!14997

We also unify conversions from and to `Gitaly::User`s in the
`Gitlab::Git::User` class.

Make pipelines table in MR view usable

See merge request gitlab-org/gitlab-ce!14941

Fix CSS in load more participants

Closes #39299

See merge request gitlab-org/gitlab-ce!15005

Refactor `have_http_status` into `have_gitlab_http_status` in the specs

Closes #35644

See merge request gitlab-org/gitlab-ce!14958

Simple docs fixes

See merge request gitlab-org/gitlab-ce!15001

Removes group_avatar & group_label_subscription from global namespace

See merge request gitlab-org/gitlab-ce!15006

Fix a small typo in the delete merged branches documentation

See merge request gitlab-org/gitlab-ce!15003

Fix the description of the new branch created by an issue's new branch button

See merge request gitlab-org/gitlab-ce!15004

Moves vue resource docs into a new file & add documentation to handle 204

Closes #39369

See merge request gitlab-org/gitlab-ce!15002