Enforce good commit messages using Danger

Closes #50003

See merge request gitlab-org/gitlab-ce!21527

Fix vertical alignment of text in diffs

Closes #48902

See merge request gitlab-org/gitlab-ce!21573

Bump Sidekiq 5.1.3 to 5.2.1

See merge request gitlab-org/gitlab-ce!21624

Bump gitlab-shell to 8.3.1

See merge request gitlab-org/gitlab-ce!21648

docs: Correct YAML indentation

See merge request gitlab-org/gitlab-ce!21631

8.3.0 was tagged with the commit before the CHANGELOG.md and
version.rb bump, so this just fixes a harmless warning.

Add `duration` attributes to Jobs API docs

See merge request gitlab-org/gitlab-ce!21626

Add changelog to !21371

See merge request gitlab-org/gitlab-ce!21615

Add /lock and /unlock quick actions

Closes #39173

See merge request gitlab-org/gitlab-ce!15197

This Dangerfile ensures that commit authors write good commit messages.
We also prevent the use of Emoji, since these add no value and may not
always be displayed properly.

Merge commits are currently ignored. In the future we most likely want
to stop using these, but this is a separate discussion, hence we ignore
them for the time being.

The rules enforced by this Dangerfile are based on the article found at
https://chris.beams.io/posts/git-commit/. For more information, refer to
https://gitlab.com/gitlab-org/gitlab-ce/issues/50003.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/50003

Replace one word in todos.md

See merge request gitlab-org/gitlab-ce!19757

Update doc: url reference to grafana

See merge request gitlab-org/gitlab-ce!21637

Clean up chart index page

See merge request gitlab-org/gitlab-ce!21623

Make topic adhere to style guide

See merge request gitlab-org/gitlab-ce!21582

Specify tar is required for backup and restore tasks

Closes omnibus-gitlab#2334

See merge request gitlab-org/gitlab-ce!21633

Merge branch 'docs/51295-update-documentation-for-interactive-web-terminals-to-remove-beta-indicator' into 'master'

Remove beta from web terminal documentation

Closes #51295

See merge request gitlab-org/gitlab-ce!21641

Document permissions for different entities

Closes #50036

See merge request gitlab-org/gitlab-ce!21109

[QA] Fix arguments passed to RSpec::Core::Runner

See merge request gitlab-org/gitlab-ce!21578

closes gitlab-org/gitlab-ce#51295

Enable frozen string for app/helpers/**/*.rb

See merge request gitlab-org/gitlab-ce!21320

Fix LDAP QA specs failing due to button change

See merge request gitlab-org/gitlab-ce!21622

Update templates and licenses for 11.3

See merge request gitlab-org/gitlab-ce!21611

Resolve "On master, inline diff view contains extra `+` and `-` signs"

Closes #51281

See merge request gitlab-org/gitlab-ce!21634

Disable query limit counter in sidekiq

See merge request gitlab-org/gitlab-ce!21470

API: Use find_branch! in all places

Closes #51250

See merge request gitlab-org/gitlab-ce!21614

Explicitly enable usage ping for instance statistics spec

Closes #51294

See merge request gitlab-org/gitlab-ce!21629

Fix QA builds failing due to change in new project page behavior

Closes gitlab-qa#322

See merge request gitlab-org/gitlab-ce!21621

This is similar to https://gitlab.com/gitlab-org/gitlab-ee/issues/7511, but
the root cause is https://gitlab.com/gitlab-org/gitlab-ce/issues/51268.

Add system note when due date is changed

Closes #38208

See merge request gitlab-org/gitlab-ce!21628

This is similar to https://gitlab.com/gitlab-org/gitlab-ee/issues/7511, but
the root cause is https://gitlab.com/gitlab-org/gitlab-ce/issues/51268.

Update invite_group_spec to be consistent with EE

See merge request gitlab-org/gitlab-ce!21608

The most significant change in this version is that the default
concurrency has been lowered from 25 to 10 (https://github.com/mperham/sidekiq/issues/3892).
This doesn't affect omnibus-gitlab because the concurrency is controlled via a
setting that defaults to 25 anyway and is passed in via the `-c` command-line
parameter.

However, source installations (including the GDK) will have to either specify
the concurrency in `sidekiq.yml` or use the `-c` option.

Full list of changes: https://github.com/mperham/sidekiq/blob/master/Changes.md