Add CI_COMMIT_MESSAGE, CI_COMMIT_TITLE and CI_COMMIT_DESCRIPTION predefined variables

Closes #20400

See merge request gitlab-org/gitlab-ce!18672

Improve UX For Group Runners

See merge request gitlab-org/gitlab-ce!18649

CE backport of Backports Push Mirrors to CE

Closes #42099

See merge request gitlab-org/gitlab-ce!18715

Cleanup pipeline build stage background migration

Closes #43854

See merge request gitlab-org/gitlab-ce!18778

Fix nginx metric names

Closes #45163

See merge request gitlab-org/gitlab-ce!18770

Client implementation GetRawChanges

See merge request gitlab-org/gitlab-ce!18693

Fix a couple of things in the security template for developers

See merge request gitlab-org/gitlab-ce!18776

Bump Gitaly to 0.98.0

See merge request gitlab-org/gitlab-ce!18740

Various improvements to repository checks

See merge request gitlab-org/gitlab-ce!18484

Part of https://gitlab.com/gitlab-org/gitaly/issues/1138

Hooks were run for wikis, but given the internal API wasn't responding
failures happended, as seen on:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/18693

Live trace: Use efficient destroy all (for `dependent: :destory` problem)

See merge request gitlab-org/gitlab-ce!18575

New CI Job live-trace architecture (v2)

Closes #44935

See merge request gitlab-org/gitlab-ce!18169

Only run session related Warden hooks for user scope

Closes gitlab-ee#5857

See merge request gitlab-org/gitlab-ce!18771

Adds changelog entry, changes RemoteMirror#sync? to be semantically sound and remove reference to pull mirrors in view

Resolve "Vuex actions - How to achieve a better state management"

Closes #44427

See merge request gitlab-org/gitlab-ce!17929

Resolve "Improve Web IDE left panel and modes"

Closes #44846

See merge request gitlab-org/gitlab-ce!18581

Upgrade underscore.js

See merge request gitlab-org/gitlab-ce!18578