Instruct users to fetch merge request branch

Instructing users to create a new branch on the target branch and then
pulling creates a few issues. If the target branch has moved on since
the source branch diverged from it, then the pull will create an
unnecessary merge commit from the target branch to the source branch. If
the user has pull.rebase set to "true" or "preserve", then this creates
an even stranger history. These instructions will ensure the local
branch created for the merge request is exactly what contributing user
has pushed.
Adds comments to commits in the API
Prepare ForkService to support forking projects to given namespaces

Remove overload of BaseService.initialize, so initialize gains params,
which is used to pass the namespace (like e.g. in TransferService).

The namespace is checked for permission to create projects in it.
Move new blob commit message textarea below editor

- match edit blob view
- you enter the commit message *after* you make the modifications
Add Markdown preview to more forms

Enable Markdown previews when creating and editing issues, merge
requests, and milestones, and when editing notes.
Use GET instead of POST for Markdown previews
Refactor Markdown preview tests

Create a new shared module for common issue/merge request behavior,
use `expect` syntax instead of `should`, and avoid `visible: false` in
the `have_css` matcher.
Fix Markdown preview tests

Update Spinach tests for Markdown previews for the new-ish tab UI that
replaced the old preview/edit toggle button.
Add new Markdown preview test

Add a test to make sure that Markdown previews are available when
editing an existing issue.
Fix long line in view
Fix houndci warnings
Fix more Markdown preview tests
Fix test assertions

Make sure we're asserting the correct thing when testing visible and
invisible DOM elements.
Fixed missing end-of-code line in 7.4 upgrade doc
Merge pull request #8162 from jmsche/patch-1

Fixed missing end-of-code line in 7.4 upgrade doc
Drop all Postgres sequences during backup restore
Add CHANGELOG entry for sequence drop
update changelog && bump version
Add failing test that should be green after group members api get fixed

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Split group members api

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>