title: Generate a migration file from schema.rb
body: <p>I'm looking to generate a migration file from the schema.rb. is it possible? </p>
  
  <p>I have many migration files at the moment and would like to combine everything into one master migration file.</p>
  
  <p>I also think i may have accidentally deleted a migration file at some point.</p>
  
  <p>thanks for any help</p>