Improve traceability for failed attempts of archiving traces

Closes #51502

See merge request gitlab-org/gitlab-ce!21826

Encourage MR author preparation in Code Review Guidelines documentation

See merge request gitlab-org/gitlab-ce!23360

Remove needless auto-capitalization on Wiki page titles

Closes #38317

See merge request gitlab-org/gitlab-ce!23288

Add config to prohibit impersonation

See merge request gitlab-org/gitlab-ce!23338

Make RemoteMirror's only_protected_branches default value consistent

See merge request gitlab-org/gitlab-ce!23410

Added frontend GraphQL docs

See merge request gitlab-org/gitlab-ce!23405

Adds gitlab.impersonation_enabled config option defaulting to true to
keep the current default behaviour.

Only the act of impersonation is modified, impersonation token
management is not affected.

Add a rebase API endpoint for merge requests

Closes #33705

See merge request gitlab-org/gitlab-ce!23296

commit 10456b1e9240886432f565dd17689080bbb133b9
Merge: 312c1a9bdf8 a5f46278
Author: Shinya Maeda <shinya@gitlab.com>
Date:   Thu Nov 29 14:33:21 2018 +0900

    Merge branch 'master-ce' into add-counter-for-trace-chunks

commit 312c1a9bdf8efc45c3fed5ff50f05cc589bbb4ed
Author: Shinya Maeda <shinya@gitlab.com>
Date:   Wed Nov 28 20:06:18 2018 +0900

    Fix coding offence

commit e397cc2ccc1b2cf7f8b3558b8fa81fe2aa0ab366
Author: Shinya Maeda <shinya@gitlab.com>
Date:   Wed Nov 28 14:40:24 2018 +0900

    Fix tracking archive failure

Update documentation with note regarding restoring ssh host keys

See merge request gitlab-org/gitlab-ce!23392

Bump gitlab-shell to 8.4.3

See merge request gitlab-org/gitlab-ce!23429

Update Knative IP address docs

See merge request gitlab-org/gitlab-ce!23380

[11.5] Fix SSRF in project integrations

See merge request gitlab/gitlabhq!2611

[master] Resolve: "Provide email notification when a user changes their email address"

See merge request gitlab/gitlabhq!2587

[master] Resolve "Reflected XSS in OAuth Authorize window due to redirect_uri allowing arbitrary protocols"

See merge request gitlab/gitlabhq!2572

[master] Fix CRLF issue in UrlValidator

See merge request gitlab/gitlabhq!2627

[master] Resolve "Personal access token with only `read_user` scope can be used to authenticate any web request"

See merge request gitlab/gitlabhq!2583

[master]Fixed ability to comment on and edit/delete comments on locked or confidential issues

See merge request gitlab/gitlabhq!2612

[master] [pages] Possible symlink time of check to time of use race condition

Closes #2742

See merge request gitlab/gitlabhq!2638

[master] XSS in markdown following unrecognized HTML element

Closes #2732

See merge request gitlab/gitlabhq!2599

[master] Fix XSS in mermaid diagrams

See merge request gitlab/gitlabhq!2597

[master] Don't expose confidential information in commit message list

See merge request gitlab/gitlabhq!2626

[master] Resolve: Promoting a milestone is missing an authorization check

See merge request gitlab/gitlabhq!2598

[master] Do not follow redirects in prometheus service

See merge request gitlab/gitlabhq!2617

[master] Stored XSS for Environments

Closes #2727

See merge request gitlab/gitlabhq!2594

[master] Fixed read private group names

See merge request gitlab/gitlabhq!2589

[Master] Redact sensitive information on gitlab-workhorse log

See merge request gitlab/gitlabhq!2584

See https://gitlab.com/gitlab-org/gitlab-shell/blob/master/CHANGELOG

[master] Resolve: "Provide email notification when a user changes their email address"

See merge request gitlab/gitlabhq!2587

[master] Resolve "Reflected XSS in OAuth Authorize window due to redirect_uri allowing arbitrary protocols"

See merge request gitlab/gitlabhq!2572

Externalize strings from `/app/views/snippets`

See merge request gitlab-org/gitlab-ce!23351

Make add_reference cop accept a hash for :index

See merge request gitlab-org/gitlab-ce!23375

Bump GitLab Workhorse to 7.2.1

See merge request gitlab-org/gitlab-ce!23424