Create main branch if no branches exist

Currently when we create a branch and the repo is empty
`master` branch is created by default.

Let's create `main` branch in this case instead

app/controllers/projects/branches_controller.rb

@@ -152,7 +152,7 @@ class Projects::BranchesController < Projects::ApplicationController
       ref_escaped = strip_tags(sanitize(params[:ref]))
       Addressable::URI.unescape(ref_escaped)
     else
-      @project.default_branch || 'master'
+      @project.default_branch_or_main
     end
   end
 

app/services/branches/create_service.rb

@@ -2,8 +2,8 @@
 
 module Branches
   class CreateService < BaseService
-    def execute(branch_name, ref, create_master_if_empty: true)
-      create_master_branch if create_master_if_empty && project.empty_repo?
+    def execute(branch_name, ref, create_default_branch_if_empty: true)
+      create_default_branch if create_default_branch_if_empty && project.empty_repo?
 
       result = ::Branches::ValidateNewService.new(project).execute(branch_name)
 
@@ -27,13 +27,13 @@ module Branches
 
     private
 
-    def create_master_branch
+    def create_default_branch
       project.repository.create_file(
         current_user,
         '/README.md',
         '',
         message: 'Add README.md',
-        branch_name: 'master'
+        branch_name: project.default_branch_or_main
       )
     end
   end

ee/app/services/projects/update_mirror_service.rb

@@ -73,7 +73,7 @@ module Projects
         local_branch = local_branches[name]
 
         if local_branch.nil?
-          result = ::Branches::CreateService.new(project, current_user).execute(name, upstream_branch.dereferenced_target.sha, create_master_if_empty: false)
+          result = ::Branches::CreateService.new(project, current_user).execute(name, upstream_branch.dereferenced_target.sha, create_default_branch_if_empty: false)
           if result[:status] == :error
             errors << result[:message]
           end