Implement module for setting "Poll-Interval" response header.
Return 429 in ETag caching middleware when polling is disabled.

From Bullet failures in !10263

Looking at the SQL log, we see useless queries such as:

```
D, [2017-03-22T03:25:00.726710 #2629] DEBUG -- :    (235.9ms)  SELECT MAX("project_authorizations"."access_level") AS maximum_access_level, "project_authorizations"."user_id" AS project_authorizations_user_id FROM "project_authorizations" WHERE "project_authorizations"."project_id" = 13083 AND 1=0 GROUP BY "project_authorizations"."user_id"  [["project_id", 13083]]
```

- Migration in Repository#is_ancestor?

Updated some Ruby code based on comments

Use full path for moving directories when changing namespace path

See merge request !2078

Using NotebookLab library

[ci skip]

Right now, it once  a chat notifacation service has been enabled, there
is no way to limit the branches which trigger a notification. Instead of
allowing the user to specify the list, I opted to let the user check the
box if they'd only want to be notified of the default branch.

Tags are uneffected by this change.

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

This reverts merge request !10076

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

Protect server against SSRF in project import URLs

See merge request !2068

Only show public emails in atom feeds

See merge request !2066

It was possible for the `routes.name` field to be `NULL`, causing
`name_was` to be `nil` after a rename, resulting a bad first argument to
`sub` when attempting to rename descendants. This change adds a
condition to make sure `name_was` is present before attempting the
descendant update.

New Gitlab::UrlSanitizer.http_credentials_for_user method responsible
for generating a credentials hash from a user.
Signed-off-by: NRémy Coutable <remy@rymai.me>