Relative Links in the Wiki Are Broken

- [ ] #16568 (!4050) Relative links in wiki are broken
    - [x] Investigate issue

  
    - [x] Implementation / Fix

        - [x] Write (failing) tests for `WikiLinkFilter`
        - [x] Link to `./bar` should either get rewritten correctly or left alone
        - [x] Link to `./bar.md` should maybe get rewritten correctly (is left alone currently)
        - [x] Link to `bar.md` should get rewritten correctly


            - [x] Check if this indeed a bug

    - [x] Make sure CI is green
    - [x] Assign to endboss

    - [x] Wait for review

    - [x] Implement review feedback
    - [ ] Wait for merge


See merge request !4050

This MR never made it into 8.7.4.

[ci skip]

This reverts commit d1ba0986.

[ci skip]

Use a case-insensitive check to compare URI schemes

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/17299

See merge request !1965

Add if exists to drop command

Add `IF EXISTS` as a precaution. Related to gitlab-org/gitlab-ce!4020

See merge request !4100

Rake drop tables with cascade

See merge request !4020

Fix build notification on merge request page change even if the build status didn't change

## What does this MR do?
This MR contains a bugfix for #17357 which was introduced by !3998. The notification are now only shown on status changes, and not when switching between different merge requests.

## Are there points in the code the reviewer needs to double check?
Check implementation

## Why was this MR needed?
Because auf a bug introduced in !3998.

## What are the relevant issue numbers?
#17357

Closes #17357

See merge request !4086

Allow Redmine issue references to work as intended

Closes #14527 and #14894 

See merge request !4048

Use sign out path only if not empty

Fixes: https://github.com/gitlabhq/gitlabhq/issues/10066

See merge request !3989

Pass trusted_proxies to action_dispatch as IPAddrs instead of strings

Without this setting your own trusted_proxies does not work.

Fixes an issue introduce in: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3524

Fixes: https://gitlab.com/gitlab-org/gitlab-ce/issues/17004

See merge request !3970

Fix importer bug when throwing exceptions

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/15681

See merge request !3941

Initialize wikis on legacy projects during check

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/4173

Helps https://gitlab.com/gitlab-org/gitlab-ce/issues/15423

See merge request !3931

Fix the line code when importing PR review comments from GitHub

Pull Request Review Comments are comments on a portion of the unified diff.

Closes #17205

See merge request !4010

Merge request widget displays TeamCity build state and code coverage correctly again

## What does this MR do?
This MR contains a fix for a regression introduced in `8.7`. In former version, the TeamCity build status was always displayed correctly. In `8.7` the build state is still checked, but the UI is not updated correctly any longer.

## Are there points in the code the reviewer needs to double check?
The changes are quite simple, so please simply double check them.

## Why was this MR needed?
This MR is needed to make the TeamCity build status working again.

## What are the relevant issue numbers?
#17080 

See merge request !3998

Instrument methods used in email diffs

See merge request !4038

Updated spacing between notification label and button

![Screen_Shot_2016-04-28_at_11.36.26](/uploads/7b33e78e85688d96f878272ee93038ba/Screen_Shot_2016-04-28_at_11.36.26.png)

Closes #16552

See merge request !3965

Fix error when trying to create a wiki page

Closes #15527, #15569, #15623, #15630, #15637, #15653, #15870, #16558, #16875, #16987, #17016, https://github.com/gitlabhq/gitlabhq/issues/10317.

See merge request !3924

Load the "New Branch" button asynchronously

Here's how it looks like for logged in users:

![new_branch](/uploads/718e3d9016a50a0432b9541dde5ca74c/new_branch.gif)

And here it is for anonymous users (or when a new branch can't be created by a logged in user):

![new_branch_anonymous](/uploads/dce42ee6a7dd7708443cdfdb56389d46/new_branch_anonymous.gif)

See merge request !3855

Updated label links to work correctly for filtering

See !3846#note_5033951

See merge request !3920

Prevent users from deleting Webhooks via API they do not own

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/15576

See merge request !1959

[ci skip]

Prevent privilege escalation via notes API

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/15577

See merge request !1964

Fixed width of .search-location-badge as it was causing issues in Safari.

Fixed width of .search-location-badge as it was causing issues in Safari.

Fixes issue #15541 and is a minor CSS only change so [ci skip]

# Before

Safari:
![Screen_Shot_2016-04-24_at_22.35.38](/uploads/74388670fde3af94429d83b954833bd3/Screen_Shot_2016-04-24_at_22.35.38.png)

# After

Safari:
![Screen_Shot_2016-04-24_at_21.59.49](/uploads/177d0d8fda665165dff5006930604fc6/Screen_Shot_2016-04-24_at_21.59.49.png)

Chrome:
![Screen_Shot_2016-04-24_at_21.59.40](/uploads/6764cd5864901210f4f8eff4388fd6db/Screen_Shot_2016-04-24_at_21.59.40.png)

# CSS class referenced in the following files:

`./app/assets/javascripts/search_autocomplete.js.coffee`

`./app/assets/stylesheets/pages/search.scss`

…and is visible on the search bar on every page.

See merge request !3900

Fixes issue with emoji comments not showing correct emoji image

Previously it would look for the unicode character inside the award menu. But this menu might not always be there.

Now, the unicode characters are loaded onto the page in an array which the award emoji that looks in to get the correct emoji unicode character

Fixes #15512

See merge request !3885