Gem updates for security issues

- sprockets (rails dependency, but we need to specify a version to pull
  in fixes)
- sass-rails (no security issues, but required an update to meet new
  sprockets version requirement)
- rest-client (coveralls dependency)

See merge request !915

Fix changelog for !767 and !794

These changes did not make it into the 7.12.0 release. The entry for
!794 is already correctly listed for 7.12.1 so it has been removed.

See merge request !920

commit hashes are monospaced

Use a monospaced font for GFM commit and commit range references

See merge request !914

These changes did not make it into the 7.12.0 release. The entry for
!794 is already correctly listed for 7.12.1 so it has been removed.

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

Add an expect call to prevent random Spinach failure

This should help prevent getting the error:

```
Unable to find field "merge_request_title
```

This was happening probably because it takes some time after the "Compare branches" button is hit before the "New merge request" page showed up.

See merge request !882

Refactor can_be_merged logic for merge request

Some refactoring after !918

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

See merge request !919

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

Merge branches inside one repository using rugged instead of satellites
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

cc @rspeicher @DouweM

See merge request !918

Extract the longest-matching ref from a commit path when multiple matches occur

### What does this MR do?

This MR extracts the longest-matching ref from a commit path. In cases when there are multiple refs that prefix the path, the ref name is ambiguous. Using the heuristic that the longest-matching ref seems like a sensible default.

### Why was this MR needed?

Suppose there is a branch named `release/app` and a tag named `release/app/v1.0.0`. Suppose `README.md` exists in the root directory.

Let's suppose the path passed in is `release/app/v1.0.0/README.md`. There are two possible ways to interpret the ref and path:

1. ref = `release/app`, path = `v1.0.0/README.md`
2. ref = `release/app/v1.0.0`, path = `README.md`

The crux of the issue is that there is ambiguity which one is correct; both could be real possibilities. In the current implementation of `extract_ref`, GitLab gets confused and tries neither: it uses ref = `release` and path = `app/v1.0.0/README.md`. Since the file does not exist, it returns 404.

### What are the relevant issue numbers?

Closes #1839

See merge request !859

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

Closes #1839

Fix GitLab CI forking

I created MR here because gitlab.com is unreachable.

See merge request !1884

UX improvements

* make atom feed on commits page smaller so it capture less attention
* open big image 400px instead of default 40px when click on user avatar

See merge request !910

Fix consistency issue in sidebars of Project and Group Settings.

Fixes #2277

![before_after_group_settings_nav](https://dev.gitlab.org/gitlab/gitlabhq/uploads/370c701d0eff8f1f8e44cf954c75f2bf/before_after_group_settings_nav.png)

See merge request !1871

Repository#blob_at should return nil for 00000000... sha
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See merge request !916

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

Reporter role can manage issue tracker now
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See merge request !908

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

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

added note about Devise

Added note about the authentication gem used in GitLab

Because of question in https://groups.google.com/forum/#!topic/gitlabhq/G2rToah19-Q

See merge request !912

added new doc "command line commands"

Added new doc to GitLab Basics

See merge request !1880

Performance improvements after caching html fragments

* re-use event cache with other users
* cache commit fragment
* cache issue fragment in list
* cache comment parsed with markdown

See merge request !911

Fix ApplicationHelper specs

On current `master` if you run these specs by themselves, they fail. I have no idea why they work when run with other specs, but now they work all the time.

- Use the `helper` object, as per RSpec 3 standards
- Use `assign` to assign instance variables that helpers expect
- Add `StubConfiguration` support module

See merge request !906

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

- sprockets (rails dependency, but we need to specify a version to pull
  in fixes)
- sass-rails (no security issues, but required an update to meet new
  sprockets version requirement)
- rest-client (coveralls dependency)

Bump Redcarpet to 3.3.2

Closes #1911

See merge request !913

Closes #1911

There were several specs that were failing when run by themselves.

- Use the `helper` object, as per RSpec 3 standards
- Use `assign` to assign instance variables that helpers expect
- Add `StubConfiguration` support module

Just for consistency with our Capybara, DatabaseCleaner, WebMock, etc.
setups.