In this instance its subgroups, and given we can't deploy it, we
shouldn't allow it to be shown.

Fixes gitlab-org/gitlab-ce#34864

In order to avoid string manipulation or modify route params (to make them unambiguous for `url_for`), we are accepting a behavior change:

When being redirected to the canonical path for a group, if you requested a group show path starting with `/groups/…` then you’ll now be redirected to the group at root `/…`.

Note: This changes the behavior of user lookups (see the spec change) so it acts the same way as groups and projects. Unauthenticated clients attempting to access a user page will be redirected to login whether the user exists and is publicly restricted, or does not exist at all.

* Regards project-level pages config
- Nav link is now shown only if Pages is enabled for instance
- Navigation to following controllers denied if Pages disabled:
  * projects/pages_controller
  * projects/pages_domains_controller
- 'disabled' partial removed
+ Test for pages_controller introduced

The user can create a new directory on a different branch than the
source branch when the branch already exists.

add complete changelog for !8949

This reverts commit 3e991230.

# Conflicts:
#	app/models/project.rb

fixes #17508

This invalidates one test, which we've removed.

Closes #14994