Refactor `Gitlab::GitAccess`

1. Don't use case statements for dispatch anymore. This leads to a lot
   of duplication, and makes the logic harder to follow.

2. Remove duplicated logic.

    - For example, the `can_push_to_branch?` exists, but we also have a
      different way of checking the same condition within `change_access_check`.

    - This kind of duplication is removed, and the `can_push_to_branch?`
      method is used in both places.

3. Move checks returning true/false to `UserAccess`.

    - All public methods in `GitAccess` now return an instance of
      `GitAccessStatus`. Previously, some methods would return
      true/false as well, which was confusing.

    - It makes sense for these kinds of checks to be at the level of a
      user, so the `UserAccess` class was repurposed for this. The prior
      `UserAccess.allowed?` classmethod is converted into an instance
      method.

    - All external uses of these checks have been migrated to use the
      `UserAccess` class

4. Move the "change_access_check" into a separate class.

    - Create the `GitAccess::ChangeAccessCheck` class to run these
      checks, which are quite substantial.

    - `ChangeAccessCheck` returns an instance of `GitAccessStatus` as
      well.

5. Break out the boolean logic in `ChangeAccessCheck` into `if/else`
   chains - this seems more readable.

6. I can understand that this might look like overkill for !4892, but I
   think this is a good opportunity to clean it up.

    - http://martinfowler.com/bliki/OpportunisticRefactoring.html

1 files changed, 2 insertions, 2 deletions

diff --git a/app/services/commits/change_service.rb b/app/services/commits/change_service.rb
index c578097376a..ed73d8cb8c2 100644
--- a/app/services/commits/change_service.rb
+++ b/app/services/commits/change_service.rb
@@ -23,7 +23,7 @@ module Commits
     private
 
     def check_push_permissions
-      allowed = ::Gitlab::GitAccess.new(current_user, project, 'web').can_push_to_branch?(@target_branch)
+      allowed = ::Gitlab::UserAccess.new(current_user, project: project).can_push_to_branch?(@target_branch)
 
       unless allowed
         raise ValidationError.new('You are not allowed to push into this branch')
@@ -31,7 +31,7 @@ module Commits
 
       true
     end
-    
+
     def create_target_branch(new_branch)
       # Temporary branch exists and contains the change commit
       return success if repository.find_branch(new_branch)