When I write a paper, it usually goes through many versions before being submitted to a journal. I keep track of the different versions by renaming the file when I’m about to make major changes, or when I receive a new version from a coauthor. The files are named file1.tex, file2.tex, etc. where “file” is replaced by something more meaningful. It is often useful to be able to compare versions to see what changes have been made, especially when working with …