1 files changed, 12 insertions, 0 deletions
diff --git a/app/services/files/multi_service.rb b/app/services/files/multi_service.rb
index bfacc462847..eb2773733b1 100644
--- a/app/services/files/multi_service.rb
+++ b/app/services/files/multi_service.rb
@@ -20,6 +20,7 @@ module Files
 
       params[:actions].each do |action|
         validate_action!(action)
+        validate_file_status(action)
       end
     end
 
@@ -28,5 +29,16 @@ module Files
         raise_error("Unknown action '#{action[:action]}'")
       end
     end
+
+    def validate_file_status(action)
+      return unless action[:last_commit_id]
+
+      current_commit = Gitlab::Git::Commit.last_for_path(
+        @start_project.repository, @start_branch, action[:file_path])
+
+      if current_commit.sha != action[:last_commit_id]
+        raise_error("The file has changed since you started editing it: #{action[:file_path]}")
+      end
+    end
   end
 end