Source code rules - MVC

Problem to solve

Based on the results of #342086 (closed) it has been determined we should organize rules based on branches. While still potentially complex, this issue represents the "boring" solution of applying that organizational system while applying current feature functionality and UI where possible.

Proposal

Add section Branch rules after section Default branch (Settings > Repository Settings > Branch rules)

Acceptance criteria

• There should be an All branches option
  • Applies to all branches
  • Is non-removable
  • Should be displayed at the top of the branch list
• Branch selection field
  • Should function similar to protected branches branch selection field
  • The dropdown list should be populated with available branches
  • The dropdown list should exclude branches with existing rules
  • The dropdown should allow for creating wild card selections
• Rules should be applied by the most permissive
  • If either a wildcard or specific branch rule grants permission, the user is allowed to perform the action
  • Merge request approvals must satisfy all required approvals
• When the merge request feature is disabled:
  • Hide the Merge request approvals section
  • Do not display Approvals in the branch rules list rules column
  • Merge request approvals would not be applicable

Description	Mockup
Branch rules section
Edit rule form
Add/Edit approval rule form modal