Fix creation of merge requests for orphaned branches with images

When attempting to create a merge request from an orphaned branch (e.g. this happens for the first commit of any repo) that contained images, GitLab would fail with a Error 500. This MR fixes that problem.

Closes #14875

See merge request !3511

Added 8.7 install/update guides

See merge request !3517

[ci skip]

Closes #14875

Improve rendering performance of Banzai

Related issues:

* gitlab-org/gitlab-ce#14315
* gitlab-org/gitlab-ce#13651

TODO:

* [x] `Banzai::Filter::ExternalIssueReferenceFilter#call` calls `Project#default_issues_tracker?` which runs a query on every call. Memoizing this only works if the `Project` instance is shared between instances of this filter. Either way it should at most only run this method once.
* [x] Fix the two failing specs
* [x] Clean of the various `call` methods in the filters where I inlined methods
* [x] Remove the `replace_XXX` methods in ReferenceFilter now that they're no longer used.

See merge request !3389

Cleaning this up any further is a bit tricky as the caches in question
should only be evaluated if RequestStore is actually enabled.

Fix bug related to filtering Issues by Label/Milestone.

See merge request !3499

Every object processed by ExternalIssueReferenceFilter can return a
different Project instance when calling "project". For example, every
note processed will have it's own associated Project. If we were to
cache Project#default_issues_tracker? on Project level this would have
no impact on Markdown rendering timings as the cache would have to be
built for every Project instance without it ever being re-used.

To work around this we cache Project#default_issues_tracker? in
Banzai::Filter::ExternalIssueReferenceFilter using the project's _id_
instead of the whole object. This setup allows re-using of the cached
data even when the Project instances used are different, as long as the
actual project IDs are the same.

For an issue with around 200 notes this cuts down timings by around 150
milliseconds.

These methods always return the same data for every class so there's no
point in computing their values on every call.

These filters now use a single iteration over all the document nodes
instead of multiple ones. This in turn allows variables to be re-used
(e.g. links only have to be unescaped once). Combined with some other
refactoring this can drastically reduce render timings.

This was originally suggested by @ayufan and modified to be a bit
cleaner and use RequestStore instead of a regular Hash.

By caching the output of the two methods involved the number of queries
is reduced significantly. For example, for an issue with 200 notes (of
which 100 reference a number of merge requests) this cuts down the
amount of queries from around 6300 to around 3300.

Build updates

Fixes #10851 

![build-updates](/uploads/52e09e679ca457f3d818f9a12fd8382b/build-updates.gif)


See merge request !2604

Add endpoints for archiving and unarchiving

Closes #14296

See merge request !3372

Don't fetch any tags from a forked repo

Closes #13957

See merge request !3504

  This problem only was affecting the dev env.

Two level hierarchy  in navigation sidebar
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See merge request !3494

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

Closes #13957

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

Remove 1px whitespace between nav tabs and underline when form present
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See merge request !3489

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

Notes/discussions header

Part way towards getting the design for issues/merge requests to look more like the design in #3401 - I have standardised the headers for both issues & merge requests comments and discussions.

See merge request !3441

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

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

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

Added & use Gitlab::Routing for URL helpers

Extracted from !3389

See merge request !3486

[ci skip]
Signed-off-by: Rémy Coutable <remy@rymai.me>

Memoize reference_pattern/link_reference_pattern

Extracted from !3389

See merge request !3485

spec and fix for fogbugz lonely user problem

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/14766

I encountered this issue while manually testing all import types for
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3066

This is really due to a horrible API

```
{ 'people' => { 'person' => array_of_people_or_single_person_as_hash } }
```

See merge request !3457

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

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

Revert "Merge branch 'users_should_not_be_able_upvote_downvote' into 'master'"

This reverts merge request !3406

See merge request !3491

Allow temp-oauth-email as notification email

Closes #14559 

/cc @dblessing @rymai 

See merge request !3477

This reverts merge request !3406

Prevent users from being able to both upvote and downvote

closes #14480 

![thumbs](/uploads/d0d64f08dbf271fe969b44c68f424123/thumbs.gif)

See merge request !3406

Fix divider in dropdown when not needed

closes #14533
## Before
![Screen_Shot_2016-03-25_at_12.35.21_AM](/uploads/20f386c9c45c9ee8716835ccfa0066ed/Screen_Shot_2016-03-25_at_12.35.21_AM.png)

## After
![Screen_Shot_2016-03-25_at_12.37.27_AM](/uploads/22db62db920017da5fe1da7670fbbb0e/Screen_Shot_2016-03-25_at_12.37.27_AM.png)

See merge request !3394

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