Also:
* Stub out index view
* Adds the clusters before_action that returns all clusters

Prepares the controller for handling multiple clusters instead of just
one.

Backport delete epic changes

Closes #40162

See merge request gitlab-org/gitlab-ce!15414

Change logic of repo name and slugs in docs review script

See merge request gitlab-org/gitlab-ce!15395

Use relative git object paths to construct absolute ones before setting Env

See merge request gitlab-org/gitlab-ce!15376

Add basic docs for troubleshooting database problems

See merge request gitlab-org/gitlab-ce!15416

Add readme only default project view preference

See merge request gitlab-org/gitlab-ce!15415

Add an attributes bag class as a GitalyClient helper

See merge request gitlab-org/gitlab-ce!15346

Update container repository path reference

Closes #40199

See merge request gitlab-org/gitlab-ce!15417

Resolve "Clicking on GPG verification badge jumps to top of the page"

Closes #40198

See merge request gitlab-org/gitlab-ce!15407

We should allow to use double underscore in the path, and it seems that
our container repository path regexp was outdated.

See https://github.com/docker/distribution/blob/master/reference/regexp.go

Fix Typo in environment create definition

See merge request gitlab-org/gitlab-ce!15413

We need to make room for Runner and Omnibus docs.
This change makes sure the correct values are defined
based on CI_PROJECT_NAME.

The option to choose readme only as a users default project view was
restored in !14900

Resolve "Follow-up from "Enable multiple queries per Prometheus graph""

Closes #39861

See merge request gitlab-org/gitlab-ce!15363

Resolve "npm list errors for gitlab-svgs and node-pre-gyp"

Closes #40020

See merge request gitlab-org/gitlab-ce!15340

Update Emoji digests and assets with latest from Gemojione v3.3.0

Closes #32634

See merge request gitlab-org/gitlab-ce!15390

Truncate tree to max 1,000 items and display notice to users

Closes #39746

See merge request gitlab-org/gitlab-ce!15333

Merge branch '40122-only-one-note-webhook-is-triggered-when-a-comment-with-time-spent-is-added' into 'master'

Resolve "Only one note webhook is triggered when a comment with time spent is added"

Closes #40122

See merge request gitlab-org/gitlab-ce!15381

Fix gitlab:backup rake for hashed storage based repositories

Closes #39573

See merge request gitlab-org/gitlab-ce!15400

Merge branch '40186-the-ee_compat_check-job-sometimes-fail-on-the-git-apply-3way-step-for-forks' into 'master'

Always fetch master from the canonical remote

Closes #40186

See merge request gitlab-org/gitlab-ce!15399

fix typo

See merge request gitlab-org/gitlab-ce!15374

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

Rendering ten thousands of tree items consumes a lot of server
time and can cause timeouts in extreme cases. Realistically,
displaying more than 1,000 files is probably not useful so
truncate and show the user a notice instead. 'Find files' can be
used to locate specific files beyond the 1,000 limit.

This way, if a fork's master branch is far behind the canonical's
master, it won't use the tip of the fork's master branch as merge base
and thus won't create a huge and wrong patch file.
Signed-off-by: Rémy Coutable <remy@rymai.me>