Adds suppport for HTML 5 details and summary tags (https://github.com/vmg/redcarpet/issues/578)

Also adds details/summary tags to Copy-as-GFM

removes redundant code from gitlab database file

See merge request !9282

Fix issues mentioned but not closed for JIRA

Closes #26028

See merge request !9687

Use gitlab-workhorse 1.4.0

See merge request !9724

Set max for Zen mode textarea to screen height

Closes #28704

See merge request !9667

Improve IssuableFinder performance

Closes #25503

See merge request !9030

Fixed spacing in mobile secondary nav

See merge request !9657

Remove "subscribed" field from API responses returning list of issues or merge requests

Closes #22374

See merge request !9661

Add gitaly server dependency

Closes gitaly#109

See merge request !9722

The `ReferenceExtractor` would return an array of `ExternalIssue`
objects, and then perform `Array#-` to remove the issues
closed. `ExternalIssue`s had `==` defined, but not `hash` or `eql?`,
which are used by `Array#-`.

Bug fixes, Gitaly gRPC support, experimental Redis integration.

Improve pipeline triggers API

See merge request !9713

In GitLab 9.0.0 we want to turn on Gitaly in Omnibus installations.
Gitaly is not a required component yet for source installations
because we want to iterate on the configuration and architecture some
more. Omnibus installations will have the option to completely disable
Gitaly if they want to or if necessary.

The new GITALY_SERVER_VERSION file which version of the Gitaly server
application is needed by the current GitLab version.

Remove remnants of git annex

See merge request !9508

Resolve "Improve Omnibus-Mattermost Command installation flow"

See merge request !9257

Delete artifacts for pages unless expiry date is specified

See merge request !9716

Fix json response in branches controller

Closes #28898

See merge request !9710

Use ETag to improve performance of issue notes polling

Closes #27582

See merge request !9036

Change language for testing colour fallback

See merge request !9537

Update profiles/account view to display new username

Closes #28655

See merge request !9650

Enable build job for caching Gems of GitLab EE

See merge request !9712

Remove es6 file extension from JavaScript files

See merge request !9241

Review changes