Add service that runs after branch removed hooks

app/services/after_branch_delete_service.rb

+require_relative 'base_service'
+
+##
+# Branch can be deleted either by DeleteBranchService
+# or by GitPushService.
+#
+class AfterBranchDeleteService < BaseService
+  attr_reader :branch_name
+
+  def execute(branch_name)
+    @branch_name = branch_name
+
+    stop_environments
+  end
+
+  private
+
+  def stop_environments
+    Ci::StopEnvironmentService
+      .new(project, current_user)
+      .execute(branch_name)
+  end
+end

app/services/delete_branch_service.rb

@@ -22,6 +22,7 @@ class DeleteBranchService < BaseService
     end
 
     if repository.rm_branch(current_user, branch_name)
+      execute_after_branch_delete_hooks(branch_name)
       success('Branch was removed')
     else
       error('Failed to remove branch')
@@ -47,4 +48,12 @@ class DeleteBranchService < BaseService
       "#{Gitlab::Git::BRANCH_REF_PREFIX}#{branch.name}",
       [])
   end
+
+  private
+
+  def execute_after_branch_delete_hooks(branch_name)
+    AfterBranchDeleteService
+      .new(project, current_user)
+      .execute(branch_name)
+  end
 end

app/services/git_push_service.rb

@@ -49,10 +49,7 @@ class GitPushService < BaseService
       update_gitattributes if is_default_branch?
     end
 
-    # Update merge requests that may be affected by this push. A new branch
-    # could cause the last commit of a merge request to change.
-    update_merge_requests
-
+    execute_related_hooks
     perform_housekeeping
   end
 
@@ -62,14 +59,24 @@ class GitPushService < BaseService
 
   protected
 
-  def update_merge_requests
-    UpdateMergeRequestsWorker.perform_async(@project.id, current_user.id, params[:oldrev], params[:newrev], params[:ref])
+  def execute_related_hooks
+    # Update merge requests that may be affected by this push. A new branch
+    # could cause the last commit of a merge request to change.
+    #
+    UpdateMergeRequestsWorker
+      .perform_async(@project.id, current_user.id, params[:oldrev], params[:newrev], params[:ref])
 
     EventCreateService.new.push(@project, current_user, build_push_data)
     @project.execute_hooks(build_push_data.dup, :push_hooks)
     @project.execute_services(build_push_data.dup, :push_hooks)
     Ci::CreatePipelineService.new(@project, current_user, build_push_data).execute
     ProjectCacheWorker.perform_async(@project.id)
+
+    if push_remove_branch?
+      AfterBranchDeleteService
+        .new(project, current_user)
+        .execute(branch_name)
+    end
   end
 
   def perform_housekeeping