Sometimes requires running `mix format` twice

[pguillory]

I love this library! Didn't realize how annoying the lack of trailing commas was until I installed this and got to have them again.

However one issue. I have a Git hook that verifies Elixir files are formatted correctly with mix format --check-formatted. Sometimes I run git commit and it fails, so I mix format && git add -p and try again, working as intended. However, since installing freedom_formatter, I noticed sometimes I have to do that twice. Here is a repro:

list = [:long_word, :long_word, :long_word, :long_word, :long_word, :long_word, :long_word, :long_word]

mix format

list = [
  :long_word,
  :long_word,
  :long_word,
  :long_word,
  :long_word,
  :long_word,
  :long_word,
  :long_word    # note no trailing comma
]

mix format

list = [
  :long_word,
  :long_word,
  :long_word,
  :long_word,
  :long_word,
  :long_word,
  :long_word,
  :long_word,   # now the trailing comma is there
]

It's not a huge deal, I guess I'll make an alias or something to do mix format twice, but it would be nice if you only had to run it once. Is that possible?