Could you point me to the line of code to trigger an automatic rename if a file already exists upon upload?

 

Currently:

fileA.xxx exists on server, new upload of fileA.xxx overwrites original fileA.xxx

 

What I'd like to see:

fileA.xxx exists on server, new upload of fileA.xxx. User gets notified of duplicate filename and is requested to either OVERWRITE the original, RENAME the uploaded file to fileA-1.xxx or CANCEL the upload.

 

or at the very least: 

fileA.xxx exists on server, new upload of fileA.xxx gets renamed to fileA-1.xxx. User get's notified of the rename