Restricted visibility levels - bug fix and new feature
This allows admin users to override restricted visibility settings when creating and updating projects and snippets, and moves the restricted visibility configuration from gitlab.yml to the web UI. See #1903.
## Move configuration location
I added a new section to the application settings page for restricted visibility levels. Each level has a checkbox, styled with Bootstrap to look like a toggle button. A checked box means that the level is restricted. I added a glowing text shadow and changed the background color for checked buttons because the default styles made it hard to distinguish between checked and unchecked. This image shows the new section with the "Public" box checked:
## Allow admins to override
To allow admin users to override the restricted visibility levels, I had to remove the `visibility_level` validation from the `Project` class. The model doesn't know about the `current_user`, which should determine whether the restrictions can be overridden. We could use the creator in the validation, but that wouldn't work correctly for projects where a non-admin user is the creator and an admin tries to change the project to a restricted visibility level.
The `Project::UpdateService` and `Project::CreateService` classes already had code to determine whether the current user is allowed to use a given visibility level; now all visibility level validation is done in those classes. Currently, when a non-admin tries to create or update a project using a restricted level, these classes silently set the visibility level to the global default (create) or the project's existing value (update). I changed this behavior to be more like an Active Model validation, where using a restricted level causes the entire request to be rejected.
Project and personal snippets didn't have service classes, and restricted visibility levels weren't being enforced in the model or the controllers. The UI disabled radio buttons for restricted levels, but that wouldn't be difficult to circumvent. I created the `CreateSnippetService` and `UpdateSnippetService` classes to do the same restricted visibility check that the project classes do. And since I was dealing with snippet visibility levels, I updated the API endpoints for project snippets to allow users to set and update the visibility level.
## TODO
* [x] Add more tests for restricted visibility functionality
cc @sytse @dzaporozhets
See merge request !1655
Enhance Markdown linebreak docs
The "Line Breaks" section within the Markdown docs was missing an example of creating a line break within a paragraph by ending a line with two spaces.
See merge request !335
Emoji cheatsheet fix
Worked through the help text for emoji to properly reference and use EmojiOne tags. Removed the ninja and reworked the first sentence a bit, as ninja isn't supported by EmojiOne. Should resolve ticket #953.
See merge request !384
Dmitriy Zaporozhets
Marin Jankovski
Dmitriy Zaporozhets
Sytse Sijbrandij
Stan Hu
Vinnie Okada
Hannes Rosenögger
Marc Radulescu
Valery Sizov
Marin Jankovski
Cameron Banga
Job van der Voort
Kuo-Cheng Yeu
Ewan Edwards
