support renaming/moving files

[DetachHead]

maybe a command line option to rename a file which updates all instances of it in the baseline

[KotlinIsland]

Would be better than re-baselineing because it wouldn't add new baseline entries, just move the old ones

What about renaming classes and functions?

[KotlinIsland]

The suggestion #134 (comment) of using version control information could be applied here.