create a unique filename from the supplied argument
local df = require "lib/dtutils.file" local result = df.create_unique_filename(filepath)
filepath - string - the path and filename requested
create_unique_filename takes a requested filepath and checks to see if it exists. If if doesn’t then it’s returned intact. If it already exists, then a two digit increment is added to the filename and it is tested again. The increment keeps increasing until either a unique filename is found or there have been 100 attempts.
result - string - the incremented filename
create_unique_filename will only attempt 100 increments.