title: Don't delete firebase cloud funtions
body: <p>I'm configuring CD process on gitlab to google cloud functions (firebase).
  Also i have 3 envs (development, staging and production) and i want to deploy each function with matching postfix (_development, _staging).</p>
  
  <p>When i deploy functions to development, for instance, from my local machine with command</p>
  
  <blockquote>
    <p>firebase deploy --only functions</p>
  </blockquote>
  
  <p>it always asks me</p>
  
  <blockquote>
    <p>Would you like to proceed with deletion? Selecting no will continue the rest of the deployments.</p>
  </blockquote>
  
  <p>And i choose "No", because i don't want to delete existing functions with other postfixes. But on gitlab there is no possibility to enter "No" and it decides to delete all that functions as default.</p>
  
  <p>Is there some solution to not delete existing functions in cloud? Probably some flag in <strong>deploy</strong> command?</p>