Include instructions to update /etc/default/gitlab

See merge request !9926

We were missing some info on updating /etc/default/gitlab

In particular, changes needed to be made in order for Pages to work,
see https://gitlab.com/gitlab-org/gitlab-ce/issues/29372

[ci skip]

Move all Pages related content to a single location

See merge request !9695

Fix creating a file in an empty repo using the API

Closes #28626

See merge request !9632

This reverts commit 4b692487.

This reverts commit 071bf3b7.

Small improvements for Cycle Analytics

See merge request !9153

Show milestone ID in a consistent way

Closes #23602

See merge request !8820

Default to dangerous MR merge button

Closes #28010

See merge request !9245

Fix the redirect to custom home page URL and move it to RootController

Closes #28609

See merge request !9518

Don't copy tooltip when copying GFM

Closes #28802

See merge request !9563

Fix Cycle Analytics -> Plan is loading forever

Closes #27622

See merge request !9577

Don't declare constants in Struct

Closes #28808

See merge request !9582

Disable the inheritance column of services in DisableInvalidServiceTemplates migration

Closes #28850

See merge request !9613

The frontend should use the v3 API for now

Closes #28863 and #28853

See merge request !9614

Add changelog for !9614

See merge request !9626

Fix creating a file in an empty repo using the API

Closes #28626

See merge request !9632

Fix cherry-picking or reverting through an MR

Closes #28711 and #28426

See merge request !9640

Update Rubyzip to 1.2.1

Closes #28933

See merge request !9660

Revert "Disallow system notes for closed issuables"

Closes #28207

See merge request !9673

8-17-stable Revert all yarn changes except for yarn.lock

See merge request !9689

This reverts commit dab6e029, reversing
changes made to bab14bdb.

Pick Yarn support into 8.17

See merge request !9591

[ci skip]

Fix concurrent access on builds/register

See merge request !9600

Expire all webpack assets by altering filename postfix

See merge request !9602

[ci skip]