This reverts commit ec4730478b798270781257913ee4cede673d4d4e.

This implements Repository#ambiguous_ref? and checks if a ref is
ambiguous before trying to resolve the ref in Project#protected_for?

Reworks Project#resolve_ref to return Gitlab::Git::Branch,
Gitlab::Git::Tag or raise an AmbiguousRef error.

CE Backport: Epic issue list and related issue list re-design

See merge request gitlab-org/gitlab-ce!23658

Resolve "Navigating unresolved discussions on Merge Request page"

Closes #51122

See merge request gitlab-org/gitlab-ce!22789

Resolve "Extended user centric tooltips"

Closes #50157

See merge request gitlab-org/gitlab-ce!23231

[CE] Backport SAML unlink changes: UrlBlocker#ascii_only

See merge request gitlab-org/gitlab-ce!23627

Resolve "Utilize new charting library for metrics dashboard"

See merge request gitlab-org/gitlab-ce!23459

Integrate csslab

Closes csslab#1

See merge request gitlab-org/gitlab-ce!23521

Fix for incorrect Correlation-ID key being passed through GRPC metadata

Closes #55054

See merge request gitlab-org/gitlab-ce!23666

Add Kushal to frontend CODEOWNERS

See merge request gitlab-org/gitlab-ce!23664

Fill project_repositories for hashed storage projects

Closes #48527

See merge request gitlab-org/gitlab-ce!23482

Replace the metrics dashboard graph with
GitLab UI's area chart component

Disable docs lint internal_links check

Closes #55038

See merge request gitlab-org/gitlab-ce!23665

Changed frontmatter filtering to support YAML, JSON, TOML, and arbitrary languages

Closes #52007

See merge request gitlab-org/gitlab-ce!23331

This check never worked once the global navigation changes were rolled
out in https://gitlab.com/gitlab-com/gitlab-docs/merge_requests/362. The
global nav will ALWAYS include /ce and /ee links, and the CE and EE
repos will never include documentation for both.  gitlab-docs now
expects the documentation to be in the following directories:

* /tmp/gitlab-docs/ce (CE)
* /tmp/gitlab-docs/ee (EE)
* /tmp/gitlab-docs/omnibus (Omnibus)

The problem is that the CE and EE repos will only include one of the
first two.

Let's disable this check until
https://gitlab.com/gitlab-com/gitlab-docs/issues/305 is resolved.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/55038

Resolve "Hide variables in UI by default"

Closes #20422

See merge request gitlab-org/gitlab-ce!23518

[CE] - Add milestones autocomplete for epics

See merge request gitlab-org/gitlab-ce!23660