How to deploy some functions to Cloud Functions for Firebase without affecting some other functions?

Question

Firebase CLI tools 3.8.0 has added the ability to deploy specific functions.

firebase deploy --only functions:func1,functions:func2

--only <targets>     
only deploy to specified, comma-separated targets (e.g. "hosting,storage"). For functions, 
can specify filters with colons to scope function deploys to only those functions (e.g. "--only functions:func1,functions:func2"). 
When filtering based on export groups (the exported module object keys), use dots to specify group names 
(e.g. "--only functions:group1.subgroup1,functions:group2)"

The following way worked for me to deploy a particular function without affecting my other functions, where "specificFunctionName" is the function I wanted to deploy

firebase deploy --only functions:specificFunctionName

firebaser here

There is currently no way to deploy a single function with the Firebase CLI. Running `firebase deploy` will deploy all functions.

We've recently discussed deploying subsets of the functions, but it's not available at the moment - nor can we give a ballpark of if/when it might be.

Update Since Firebase CLI release the ability to deploy single functions is available. See yuku's answer.

firebase deploy --only "functions:<fileName>.<functionName>"

example folder structure:

functions 
  node_modules
  index.js
  smsNotification.js
  ...

You can redeploy just a function in a file with

firebase deploy --only "functions:smsNotification.sendChatNotif"

You can redploy all functions in a file with

firebase deploy --only "functions:smsNotification"