Have `Project#open_branches` return branches that are matched by a wildcard protected branch.

1. The `open_branches` method is used to provide a list of branches
   while creating a protected branch.

2. It makes sense to include branches which are matched by one or more
   wildcard protected branches, since the user might want to make exact
   protected branches from these as well.

3. This also provides a large performance improvement. On my machine, in
   a project with 5000 branches and 2000 protected branches, the
   `ProtectedBranches#index` page went from a 40 seconds load time to 4
   seconds (10x speedup).

app/models/project.rb

@@ -802,8 +802,12 @@ class Project < ActiveRecord::Base
     @repo_exists = false
   end
 
+  # Branches that are not _exactly_ matched by a protected branch.
   def open_branches
-    repository.branches.reject { |branch| self.protected_branch?(branch.name) }
+    exact_protected_branch_names = protected_branches.reject(&:wildcard?).map(&:name)
+    branch_names = repository.branches.map(&:name)
+    non_open_branch_names = Set.new(exact_protected_branch_names).intersection(Set.new(branch_names))
+    repository.branches.reject { |branch| non_open_branch_names.include? branch.name }
   end
 
   def root_ref?(branch)

app/models/protected_branch.rb

@@ -34,7 +34,7 @@ class ProtectedBranch < ActiveRecord::Base
 
   # Checks if this protected branch contains a wildcard
   def wildcard?
-    self.name.include?('*')
+    self.name && self.name.include?('*')
   end
 
   protected

spec/models/project_spec.rb

@@ -438,12 +438,12 @@ describe Project, models: true do
     it { expect(project.open_branches.map(&:name)).to include('feature') }
     it { expect(project.open_branches.map(&:name)).not_to include('master') }
 
-    it "does not include branches matching a protected branch wildcard" do
+    it "includes branches matching a protected branch wildcard" do
       expect(project.open_branches.map(&:name)).to include('feature')
 
       create(:protected_branch, name: 'feat*', project: project)
 
-      expect(Project.find(project.id).open_branches.map(&:name)).not_to include('feature')
+      expect(Project.find(project.id).open_branches.map(&:name)).to include('feature')
     end
   end