Fix push rules on Git 2.11

Closes #1736

See merge request !1525

Update Geo docs to reflect what is synced

[ci skip]

See merge request !1603

Order GeoNodes by ID to keep them in the same place

See merge request !1611

Resolve "Making it easier to configure approvals in project settings"

Closes #1738

See merge request !1527

Add information about namespace encoding to API docs

See merge request !1612

[ci skip]

Starting with Git 2.11:

 * In order for the receiving end of "git push" to inspect the
   received history and decide to reject the push, the objects sent
   from the sending end need to be made available to the hook and
   the mechanism for the connectivity check, and this was done
   traditionally by storing the objects in the receiving repository
   and letting "git gc" expire them.  Instead, store the newly
   received objects in a temporary area, and make them available by
   reusing the alternate object store mechanism to them only while we
   decide if we accept the check, and once we decide, either migrate
   them to the repository or purge them immediately.

This means that some special environment variables
(`GIT_OBJECT_DIRECTORY`, and `GIT_ALTERNATE_OBJECT_DIRECTORIES`) need to be
set (or passed to `Rugged::Repository.new` in the `alternates` keyword
argument) in order for the new-and-no-yet-accepted objects to be
seen by the various Git commands (e.g. `rev-list` or
`Gitlab::Git::Commit#find`).
Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

Fix markdown table in API Issues docs

See merge request !1596

[EE] Remove the User#is_admin? method

See merge request !1615

Update rubocop-rspec 1.12.0 -> 1.15.0

See merge request !1609

EE port of "Start discussion"

See merge request !1556

Update droplab to webpack version ee

See merge request !1608

Port of button-capitalisation for EE

See merge request !1590

EE port of "Copy diff file path as GFM"

See merge request !1589