- Need to pass in a `page_slug` to the filter, so it can rewrite based
  on the current page (all links are rewritten to the level of the app root).
- The earlier `markdown_preview` endpoint was at the level of the wiki.
  We need to know the current page (for rewriting, as above), so this
  commit moves the endpoint to the level of a wiki page.
- Fix all tests

Redirect /namespace/project/info/refs to
/namespace/project.git/info/refs, so `git clone` works on either
namespace/project.git or namespace/project.

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

- Move the `TwoFactorAuthsController`'s `new` action to `show`, since
  the page is not used to create a single "two factor auth" anymore. We
  can have a single 2FA authenticator app, along with any number of U2F
  devices, in any combination, so the page will be accessed after the
  first "two factor auth" is created.
- Add the `u2f` javascript library, which provides an API to the
  browser's U2F implementation.
- Add tests for the JS components

No spaces before commas.

See #17478

Closes #16563

Closes #14091

Also added a health check page to the admin section for resetting the token.

This reverts commit 0a280158.

We send a state of ansi2html to client, client needs to send this state back.
The state describes the configuration of generator and position within trace.

- So that the server doesn't have to be restarted for every change in dev.

This button depends on Issue#can_be_worked_on? which in turn depends on
Issue#related_branches. By rendering this button asynchronously we can
finally remove all usages of Issue#related_branches and
Issue#referenced_merge_requests from the issues "show" page.

Sent emails in the development environment will no longer automatically
be opened in the browser. If a sent email needs to be viewed, it can be
found at the `/rails/letter_opener` route.

Closes #4228

Issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/12785
Merge Request: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3514

Report: https://github.com/gitlabhq/gitlabhq/issues/10138Signed-off-by: Rémy Coutable <remy@rymai.me>

Currently this works by loading the HAML partials via XHR. While this is
not the nicest setup it _is_ the easiest setup using the tools we
currently have.

Loading this data asynchronously doesn't make loading the related
MRs/branches itself faster, it merely ensures that loading the issue
itself is not slowed down.

Fixes gitlab-org/gitlab-ce#14949