Merge branch 'zj-format-chat-messages' of gitlab.com:gitlab-org/gitlab-ce into zj-format-chat-messages

This improves the styling and readability of the code. This is supported
by both Mattermost and Slack.

UX Guide: minor updates

See merge request !8862

[ci skip] UX guide: clean up term tables in copy

[ci skip] UX guide: update dropdown max height for multiline items

Remove hard-coded absolute URLs from all frontend assets

See merge request !8831

Fixed Issuable sidebar so it remains closed on mobile/smaller screen devices

See merge request !7466

Merge branch '27248-filtered-search-does-not-allow-filtering-labels-with-multiple-words' into 'master'

Fix filtering label and milestone with multiple words

Closes #27248 and #27334

See merge request !8830

Resolve "NameError: uninitialized constant ApplicationSetting::DEFAULTS"

Closes #27280

See merge request !8805

Merge branch '26448-unnecessary-request-is-made-when-filter-input-box-is-focused-by-keyboard' into 'master'

Only search commits on input change since last search

Closes #26448

See merge request !8488

Fix search bar search param encoding

Closes #27398

See merge request !8753

Contribution calendar now scrolls right by default

See merge request !6192

UI updates

See merge request !8669

Add rspec_profiling to the rspec environment

Closes #23034

See merge request !7854

Fixed cancel button in the services form not redirecting back to the integrations settings view

Closes #27301

See merge request !8843

Fix project name label's for reference in project settings

Closes #27259

See merge request !8795

Fix a transient failure in the `Explore::ProjectsController` spec

Closes #27350

See merge request !8847

Don't call `#uniq` on a relation

See merge request !8784

Use new partial to render a badge without a link in the builds details.

Closes #26947

See merge request !8740

Fixed merge request tabs extra margin

Closes #26853

See merge request !8841

Fix Error 500 when repositories contain annotated tags pointing to blobs

Closes #27228

See merge request !8800