Merge pull request #9298 from wangjohn/add_documentation_to_migration_collision

Added extra comment when a migration already exists of the same name

1 files changed, 1 insertions, 1 deletions

diff --git a/railties/lib/rails/generators/migration.rb b/railties/lib/rails/generators/migration.rb
index 5bf98bb6e0..cd69a017dd 100644
--- a/railties/lib/rails/generators/migration.rb
+++ b/railties/lib/rails/generators/migration.rb
@@ -52,7 +52,7 @@ module Rails
           if destination && options.force?
             remove_file(destination)
           elsif destination
-            raise Error, "Another migration is already named #{@migration_file_name}: #{destination}"
+            raise Error, "Another migration is already named #{@migration_file_name}: #{destination}. Use --force to remove the old migration file and replace it."
           end
           destination = File.join(migration_dir, "#{@migration_number}_#{@migration_file_name}.rb")
         end