Reduce SQL query counts in IssueReferenceFilter

## What does this MR do?

This MR adds a preparation phase for reference filters that allows them to prepare/create data structures used while iterating over HTML nodes. In this particular case the preparation phase is used for issue references to greatly cut down the amount of queries executed to get projects/issues for Markdown references.

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

No.

## Why was this MR needed?

Rendering Markdown containing issue references would run at most two queries for every issue reference: one to get the project and one to get the issue from said project. When rendering Markdown with lots of issue references this would result in _a lot_ of queries being executed.

## What are the relevant issue numbers?

#18042

See merge request !4410

Added title attribute to entries in tree view

## What does this MR do?

Adds a title attribute to entries in the tree view. Moe useful when files have long names.

## What are the relevant issue numbers?

Closes #18353 


See merge request !4709

Added source branch text to dropdown toggle

## What does this MR do?

Previously, the dropdown toggle would default to "Select source branch", this changes that so that it defaults to the branch name and if that doesn't exist, it defaults to "Select source branch"

## Screenshots (if relevant)

![Screen_Shot_2016-06-07_at_12.20.10](/uploads/40d31e21297a99300050cf9f23bd7371/Screen_Shot_2016-06-07_at_12.20.10.png)

See merge request !4504

Fix project header alignment media query bug

## What does this MR do?
Fixes media query bug on project header

## Screenshots (if relevant)
![Screen_Shot_2016-06-15_at_3.22.20_PM](/uploads/3d84f8ffb88c316f317048e15ffea4f3/Screen_Shot_2016-06-15_at_3.22.20_PM.png)

See merge request !4689

Add bottom padding for merge request command line text

Because without bottom padding text is too close to the UI tabs - hard to navigate



See merge request !4681

Avoid a TypeError when initializing MergeRequest JS class with no arg

## What does this MR do?

Avoid a TypeError when initializing MergeRequest JS class with no arg.

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

No.

## Why was this MR needed?

Without this sane default you would get the following error when you
tried to instantiate a new MergeRequest object with no argument (i.e.
`new MergeRequest();`):
    
    TypeError: undefined is not an object (evaluating 'this.opts.action')

## What are the relevant issue numbers?

Fixes #13525.

## Does this MR meet the acceptance criteria?

- [x] No CHANGELOG since it's a trivial internal change
- [x] Tests
  - [x] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4667

Fixed alignment of download dropdown

## What does this MR do?

Correctly aligns the download dropdown on merge requests

## Screenshots (if relevant)

![Screen_Shot_2016-06-14_at_14.47.06](/uploads/9381f25110e5573e56aa5c3f46786df5/Screen_Shot_2016-06-14_at_14.47.06.png)

See merge request !4646

Fixed last push event banner not being in container

## What does this MR do?

Adds the last push event content into a container with the correct class.

## What are the relevant issue numbers?

Closes #18567 

## Screenshots (if relevant)

![Screen_Shot_2016-06-14_at_13.17.41](/uploads/4afa3d2c73e59c5ffbd53869e49baa92/Screen_Shot_2016-06-14_at_13.17.41.png)

See merge request !4644

Fixed issue when opening a highlighted line diff

## What does this MR do?

With the new project nav being fixed, the diff page is scrolling the highlighted under the nav meaning you cant see what is highlighted. This corrects that by added the height of the new project nav into the offset.

See merge request !4597

Implements TemplateDropdown class to create custom template dropdowns

## What does this MR do?
Refactorize template dropdowns. This MR creates a base TemplateSelector class so it can be reused for multiple types of templates.

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- [ ] Tests
  - [ ] Added for this feature/bug
  - [x] All builds are passing
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4697

Shows build scroll buttons after build is complete

## What does this MR do?

Shows the build scroll buttons whenever there is a build trace. Previously they were only shown when the build was active.

## What are the relevant issue numbers?

Closes #18515 

## Screenshots (if relevant)

![Screen_Shot_2016-06-13_at_11.42.42](/uploads/6e0577f46a0cc7b4f2f13b17c85d97da/Screen_Shot_2016-06-13_at_11.42.42.png)

See merge request !4621

Fix images in emails

Closes #18474. The confirmation email is actually the only one that uses the `image_tag` helper at the moment, but this will work for all of them:
```shell
$ ag image_tag -G mailer
app/views/layouts/devise_mailer.html.haml
13:              = image_tag('mailers/gitlab_header_logo.png', id: 'logo', alt: 'GitLab Wordmark')
24:                  = image_tag('mailers/gitlab_tanuki_2x.png', alt: 'GitLab Logo')
```

See merge request !4705

Lighten each logo path color instead of white

## What does this MR do?
Changes highlight/loading colors of tanuki from white to a lighter version of each path color

## Why was this MR needed?
Since the logo is no longer on the dark sidebar, the highlight color was getting lost against the light gray background

## What are the relevant issue numbers?
Closes #18521 

## Screenshots (if relevant)
![logo](/uploads/3743925862fa8e17d2fec426f7e4c853/logo.gif)

cc @jschatz1 @lbennett @dzaporozhets 

See merge request !4690

Banzai::Filter::ExternalLinkFilter use XPath

See merge request !4702

Closes #18353

Use gitlab_git 10.1.4

Towards https://gitlab.com/gitlab-org/gitlab-ce/issues/18690,
following https://gitlab.com/gitlab-org/gitlab_git/merge_requests/87 .

See merge request !4706

This reduces the number of queries executed in IssueReferenceFilter by
retrieving the various projects/issues that may be referenced in batches
_before_ iterating over all the HTML nodes.

A chunk of the logic resides in AbstractReferenceFilter so it can be
re-used by other filters in the future.

Improve pipeline status in case that pipeline has no jobs

## What does this MR do?

This MR resolves problem with pipeline status when there are no build in pipeline.

This can happen when builds were skipped - for example - by using `only`/`except` keyword in `.gitlab-ci.yml`.

## What are the relevant issue numbers?

Closes #17977

See merge request !4403

Banzai::Filter::UploadLinkFilter use XPath

See merge request !4703

Fix permission checks in member row (backport from gitlab-org/gitlab-ee!460)

## What does this MR do?

It improves the check we use to display or not the members' access and controls in the members list.

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

No, I replaced an helper with just a permission check so I think it's a better solution.

## Why was this MR needed?

There were a spec failure in gitlab-org/gitlab-ee!460 because of the refactor done in the "request access" MR.

## What are the relevant issue numbers?

None.

## Does this MR meet the acceptance criteria?

- No CHANGELOG needed
- [x] Tests
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4670

Turn Group#owners into a has_many association

## What does this MR do?

This turns the regular method `Group#owners` into a `has_many` association.

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

As far as I can tell there's no way to do this without using an intermediate association, but perhaps I'm missing something. The reason an intermediate association is needed is because the supplied Proc is applied to the _final_ association (the one returning users), this means that when using a single `has_many` you can't filter out any intermediate rows (e.g. group members).

## Why was this MR needed?

This code being a regular method would prevent eager loading of the owners of a Group, turning it into a `has_many` association resolves this problem. This was discovered in !4410.

## What are the relevant issue numbers?

None.

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] ~~[Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)~~
- [x] ~~API support added~~
- [ ] Tests
  - [x] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4676

Make project_id nullable

## What does this MR do?
Fixes the broken migration which is not in sync with `db/schema.rb`.

It's to solve https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/469.


See merge request !4701

This allows the owners to be eager loaded where needed.

Update migration_style_guide.md with new details

See merge request !4693

[ci skip]

[ci skip]

Previously, the dropdown toggle would default to "Select source branch",
this changes that so that it defaults to the branch name and if that
doesn't exist, it defaults to "Select source branch"

Also License dropdown has been ported to use our GL dropdown instead of Select2.
Fixes tests to make it work with current implementation

Hide the Todo button in the collapsed issuable sidebar.

## What does this MR do?

Fixes a bug where the "Add Todo" button was displayed in the collapsed sidebar.

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

This shouldn't remove any other elements from the collapsed sidebar.

## What are the relevant issue numbers?

None

## Screenshots (if relevant)

Before:

![Screen_Shot_2016-06-15_at_11.41.46_AM](/uploads/27a1ace58cf8c44ad96accd3d0b32f11/Screen_Shot_2016-06-15_at_11.41.46_AM.png)

After:

![Screen_Shot_2016-06-15_at_11.40.53_AM](/uploads/91a8585680fc482682d0efafdba4d599/Screen_Shot_2016-06-15_at_11.40.53_AM.png)

See merge request !4686

Fix long commit message scroll issue.

Fixes horizontal scrollbar for long commit description.

## Before
![before_](/uploads/d261e26044d8ab451bc7768b16316253/before_.png)

## After
![after](/uploads/f27227a77d25d80b797e3ffc916d1957/after.png)

See merge request !4643

Show categorised search queries in the search autocomplete

Fixes #5885 

It works in 3 categories, Dashboard, Groups and Project.

## Dashboard context
![for-dashboard](/uploads/3a59f6ec008a972495597c8f2691c385/for-dashboard.png)

## Group context
![for-group](/uploads/f7aa413d56330a1d9b2e5562f95badf7/for-group.png)

## Project context
![for-project](/uploads/dabe04cf8758a056cf7b03da001ffd91/for-project.png)


## Screencast
![category-search-dropdown](/uploads/4d9513dcd6ccb6e24adefdf65f9bc778/category-search-dropdown.gif)



See merge request !4499