Test migration paths

## What does this MR do?

It checks out the code base at v8.0.5, seeds the database, and runs all migrations. 

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

If this might make sense, does this simulate enough what happens in the real world.

## What are the relevant issue numbers?

Closes #14549 

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4874

Better document triggers docs

## What does this MR do?

- Refactor the triggers page view
- Replace old images with new ones
- Mention triggers in `ci/yaml/README.md`

## Screenshots (if relevant)

The new triggers views contains more information and is prettier :)

## Before

![screenshot-localhost_3000_2016-09-06_10-53-10](/uploads/8f45a0e21a31f1819af1739f7af8afd0/screenshot-localhost_3000_2016-09-06_10-53-10.png)

# After

![screenshot-localhost_3000_2016-09-06_10-36-34](/uploads/2bbe2801b0f959851a8cfa5a8a14623d/screenshot-localhost_3000_2016-09-06_10-36-34.png)

## 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] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [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)

## What are the relevant issue numbers?

Closes #21773

See merge request !6217

Clean up search result classes

## What does this MR do?

Clean up search result classes

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

I checked if those methods are used and it seems like NO. But you can check as well.

## Why was this MR needed?

To be clean

See merge request !6216

This commit adds a job to the pipeline to test if migration on seed
data works. Even though the seed data is not perfect, it does give more
guarentees that this will succeed in the real world too.

seed_fu is used instead of dev:setup to save some time, as they both
generate the data in the same way, this should be fine.

Hide build spinner on canceled builds

## What does this MR do?

If the build has canceled this correctly hides the spinner

## What are the relevant issue numbers?

Closes #19651 

## Screenshots (if relevant)

![Screen_Shot_2016-07-11_at_13.51.57](/uploads/8342470cf35dae7c67168d9153592fb6/Screen_Shot_2016-07-11_at_13.51.57.png)

See merge request !5182

Remove gitorious from import_sources on ApplicationSetting model

Removes 'gitorious' as import field from the import_sources field on ApplicationSetting

Closes #21804

cc @markglenfletcher

See merge request !6180

Refactor merge requests documentation

## What does this MR do?

Add more information on merge requests.

## Moving docs to a new location?

See the guidelines: http://docs.gitlab.com/ce/development/doc_styleguide.html#changing-document-location

- [x] Make sure the old link is not removed and has its contents replaced with a link to the new location.
- [x] Make sure internal links pointing to the document in question are not broken.
- [x] Search and replace any links referring to old docs in GitLab Rails app, specifically under the `app/views/` directory.
- [x] If working on CE, submit an MR to EE with the changes as well.

---

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/21857

See merge request !6202

Move CHANGELOG entries of !5361, !5451 and !5887 from 8.11 to 8.12

## What does this MR do?

Move CHANGELOG entries of !5361, !5451 and !5887 from 8.11 to 8.12

## Why was this MR needed?

They were wrongly added to 8.11 here:

- https://gitlab.com/gitlab-org/gitlab-ce/commit/220755f52ad6e3fdfa43c62e0a4a4051721246dc#note_14900001
- https://gitlab.com/gitlab-org/gitlab-ce/commit/87f93ceb9542c415d6c23c72ff93d63272107d54

See merge request !6189

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

Fix missing flash messages on service edit page

## What does this MR do?

This MR fixes missing post-update flash notifications for service edit page. Bug was introduced in https://gitlab.com/gitlab-org/gitlab-ce/commit/76aad9b76ed756ca9ba2cbcdb399c815e542b3ae#3ca7aff54d2814b971a98a7bf2837e07ab3dfa04_21_20 and caused by passing `notice: Successfully updated.` to path helper instead of passing it to `redirect_to` due to wrong parenthesis placement.

## Why was this MR needed?

While adding HipChat integration I noticed that no messages are being displayed after clicking on "Save changes" button. I looked into code and observed that there is a code for these messages which once worked but doesn't work anymore. It's a regression which should be fixed.

## Screenshots (if relevant)

![image](/uploads/32b851e5bdc2a6438f35061473db9650/image.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [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 !6195

Safer ref updates

Use `git update-ref` to prevent clobbering concurrent ref updates. If
rugged/libgit2 is temporarily confused, due to concurrent `git gc` for
example, then it used to be possible to accidentally reset a ref to an
earlier state and lose commits. Because `git update-ref` does not get
confused by `git gc`, what will happen now is that the commit based on
confused information fails, preventing data loss.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/20353

See merge request !6130

Add documentation on template dropdowns

## What does this MR do?

Add docs for the dropdown template selectors

/cc @axil 

See merge request !4865

Update README.md

Added a line to the SSH Key Gen section, to ensure that the `before_script` does not prompt for a passphrase.

See merge request !6176

Add link on API docs index page



See merge request !6190

Fix randomly failing specs in expand_collapse_diff_spec:

This MR fixes the following random failure in a spec:

```
 Failure/Error: namespace.human_name + ' / ' + name

     ActionView::Template::Error:
       undefined method `+' for nil:NilClass
     # ./app/models/project.rb:807:in `name_with_namespace'
     # ./app/views/layouts/project.html.haml:1:in `_app_views_layouts_project_html_haml___2918737809244135908_70160161538920
'
     # ./app/controllers/projects/commit_controller.rb:23:in `show'
     # ./lib/gitlab/request_profiler/middleware.rb:15:in `call'
     # ./lib/gitlab/middleware/go.rb:16:in `call'
     # ./lib/gitlab/middleware/static.rb:9:in `call'
     # ------------------

     # --- Caused by: ---
     # NoMethodError:
     #   undefined method `+' for nil:NilClass
     #   ./app/models/project.rb:807:in `name_with_namespace'
```

Capybara's `click_link` method doesn't actually wait for the page to reload.
When the `expand_all_diffs` parameter is used, we need to search for unique
elements that appear to ensure that the page has actually reloaded.

Closes #21841

See merge request !6193

```
 Failure/Error: namespace.human_name + ' / ' + name

     ActionView::Template::Error:
       undefined method `+' for nil:NilClass
     # ./app/models/project.rb:807:in `name_with_namespace'
     # ./app/views/layouts/project.html.haml:1:in `_app_views_layouts_project_html_haml___2918737809244135908_70160161538920
'
     # ./app/controllers/projects/commit_controller.rb:23:in `show'
     # ./lib/gitlab/request_profiler/middleware.rb:15:in `call'
     # ./lib/gitlab/middleware/go.rb:16:in `call'
     # ./lib/gitlab/middleware/static.rb:9:in `call'
     # ------------------

     # --- Caused by: ---
     # NoMethodError:
     #   undefined method `+' for nil:NilClass
     #   ./app/models/project.rb:807:in `name_with_namespace'
```

Capybara's `click_link` method doesn't actually wait for the page to reload.
When the `expand_all_diffs` parameter is used, we need to search for unique
elements that appear to ensure that the page has actually reloaded.

Closes #21841