Show sub-nav under Merge Requests when issue tracker is non-default

Closes #30779

See merge request !10658

This reverts commit 22726942.

Fix recent searches icon alignment in Safari

Closes #30642

See merge request !10606

Fix the `gitlab:gitlab_shell:check` task

Closes omnibus-gitlab#1993

See merge request !10645

Fix NUMBER_OF_TRUNCATED_DIFF_LINES re-definition error

See merge request !10664

Use avatars instead of icons in activity view

See merge request !10596

Update all instances of "fa-refresh" to "fa-spinner"

Closes #22714

See merge request !10490

Indent system notes on desktop screens

Closes #30858

See merge request !10667

Fix pdflab code including file paths

See merge request !10632

Update merged icon

See merge request !10635

Prepare for zero downtime migrations

See merge request !9976

Use preload to avoid Rails using JOIN

See merge request !10666

Reset New branch button when issue state changes

Closes #21292

See merge request !5962

Add link to environments on kubernetes.md

See merge request !10555

Improve webpack-dev-server compatibility with non-localhost setups.

Closes #27729

See merge request !10604

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/30642

Fixes https://sentry.gitlap.com/gitlab/gitlabcom/issues/26786/

Fix filtered search input width for IE

Closes #30856

See merge request !10662

Add auth to topics page

See merge request !10643

Fixed missing capitalisation on buttons

See merge request !10631

Starting with GitLab 9.1.0 we will no longer allow downtime migrations
unless absolutely necessary. This commit updates the various developer
guides and adds code that is necessary to make zero downtime migrations
less painful.

Fixed random failures with Poll spec

Closes #30824

See merge request !10654

Make the `gitlab:gitlab_shell:check` task check that the repositories storage
path are owned by the `root` group
Signed-off-by: Rémy Coutable <remy@rymai.me>

Remove heading and trailing spaces from label's color and title

See merge request !10603

Include CONTRIBUTING.md file when importing .gitlab-ci.yml templates

See merge request !10653

Improve the testing documentation

Closes #29499 and #29623

See merge request !10161

Set user contribution calendar `overflow-x: scroll` more precisely

Closes #30738

See merge request !10636

removes redundant code from database.rb

Closes #29056

See merge request !10583

Improve discussion_comments_spec perf

See merge request !10648