Prevent privilege escalation via "impersonate" feature

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/15548

See merge request !1956

Fixes window.opener bug

Adds `noreferrer` value to rel attribute for external links

REF: https://gitlab.com/gitlab-org/gitlab-ce/issues/15331

See merge request !1953

See https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/1948

Fix 2FA authentication spoofing
Signed-off-by: Rémy Coutable <remy@rymai.me>

[ci skip]

Closes #13957

Bump Git version requirement to 2.7.4 (for 8.3)

[ci skip]

See merge request !3284

Fixes routing errors for /api/v3/projects/

[ci skip]

[ci skip]

[ci skip]

Fix project destroy callback

See gitlab-org/gitlab-ee!107.

See merge request !2307

Use gitlab-workhorse 0.5.3

See merge request !2367

Generate builds when creating tag using web interface

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/4296

See merge request !2366

Optimize LDAP and add a search timeout

Related to #4282 

This merge request arranges some things in `access.rb` to facilitate some optimizations in EE (to come later). It also adds a 10 second timeout to all LDAP searches so the entire worker is not blocked if some query doesn't return in a reasonable amount of time. This timeout is configurable per LDAP server.

See merge request !2267

Use WOFF versions of SourceSansPro

See https://gitlab.com/gitlab-org/gitlab-ce/issues/6023

See merge request !2357

Fix Error 500 when visiting build page of project with nil runners_token

Properly ensure that the token exists and add defensively check for a
non-nil value.

Closes #4294

See merge request !2294

Do not call API if there is no API URL

Fixes #5878 

CE users may not be interested in the new JIRA features. In this case,
we should detect they haven't set an API URL and fallback to the
behavior pre-8.3. This patch does that very easily.

There are planned improvements to JIRA in future releases such as
gitlab-org/gitlab-ce#5541 which will make this more configurable.

See merge request !2341

Add CHANGELOG entry for reply-by-email fix

[ci skip]

See merge request !2359

Suppress e-mails on failed builds if allow_failure is set

Every time I push to GitLab, I get > 2 emails saying a spec failed when I don't care about the benchmarks and others that have `allow_failure` set to `true`.

@ayufan mentioned creating a summary e-mail to prevent getting one e-mail per build, but the latter might actually be desirable. For example, I do want to know if Rubocop errors fail right away.

See merge request !2178

Get "Merge when build succeeds" to work when commits were pushed to MR
target branch while builds were running

The Merge when build succeeds service only merges when the MR is
mergeable (open, not WIP, no conflicts).

When the target branch is updated, all affected MRs have their merge
status set to `unchecked`, and the conflicts check will only happen
when `check_if_can_be_merged` is called, which happens when the MR page
is viewed.

When someone enables the automatic merge, the target branch is updated,
no-one views the MR page again, and the build succeeds, the mergeability
check will fail and the MR will not in fact be merged.

This MR makes sure `check_if_can_be_merged` is always called when MR
mergeability is checked.

See merge request !2304

This reverts commit 9c8ce4b6.

Better support for referencing and closing issues in asana_service.rb (by @mikew1)

See merge request !2302

Add DEBUG_BANZAI_CACHE env var to debug Banzai cache issue.

See https://gitlab.com/gitlab-org/gitlab-ce/issues/4130#note_3012511

See merge request !2283

Hotfix note mail with notification