Resolve "Move `lib/ci` to `lib/gitlab/ci`"

Closes #5836

See merge request !14078

Remove db/migrate/20170828135939_migrate_user_external_mail_data.rb

See merge request !14240

Update mysql_to_postgresql.md to deprecate these docs in favor of PGLoader

See merge request !14238

This file is a duplicate of a post-deploy migration and appears to have
been left in by mistake.

Looping through the Users table in a foreground migration would've been
a bad idea.

[ci skip]

Resolve "Image onion skin + swipe does not work anymore"

Closes #37730 and #37732

See merge request !14215

fix CI

fix CI

Revert "Merge branch 'revert-f2421b2b' into 'master'"

See merge request !14190

Fix Auto DevOps quick start guide

Closes #37768

See merge request !14230

Decrease Perceived Complexity threshold to 15

See merge request !14160

Decrease Cyclomatic Complexity threshold to 13

See merge request !14152

Migrate Git::CommitStats to Gitaly

Closes gitaly#519

See merge request !14077

Add developer documentation about working with sent emails and previews

See merge request !14227

Resolve "Error 500 in non-UTF8 branch names"

This could potentially "duplicate" branches on the UI, but it prevents
500 errors. The real issue here is the fact that a branch name with a
invalid UTF-8 characters.

Closes #37025

See merge request !14090

Fixed the breadcrumbs project name not having hover style

Closes #37661

See merge request !14211

Detect orphaned repositories

See merge request !14204

Allow to use same periods for housekeeping tasks

Closes #34981

See merge request !13711

Fix JS error in fly-out nav

See merge request !14212

Replace the 'project/issues/award_emoji.feature' spinach test with an rspec analog

See merge request !14202

Replace the 'project/builds/summary.feature' spinach test with an rspec analog

See merge request !14177

Eager load namespace owners for project dashboards

Closes #27376

See merge request !14188

Reset primary keys after swapping events tables

See merge request !14182

Add GitLab-Pages version to Admin Dashboard

Closes #36953

See merge request !14040

Closes #37661

Hide read_registry scope when registry is disabled on instance

See merge request !13314