I am using a dropbox api and building a code writing app for iPhone (so my space is very limited). When the user opens a file, Dropbox gets notified. If the file gets opened in another location (like on a computer) and saved, then by the time the user saves the originally opened file they may be overwriting already existing changes. I want to basically say "Hey! The file you are trying to save, has already been modified elsewhere..." They then have two choices... To create a new file out of the changes they made, or to discard their changes. Those buttons can really only be 2 very short words, but one word each button works best. "Accept changes" barely fits.
What short phrase can I use to say what I mean, and should I write on the buttons to say "create new file from changes" or "discard your file"?