Warn the user if they attempt to save a pretty printed log over the top of the original file

[GaryHughes]

[gnbond]

I noticed this most when quitting VSCode with a pretty-printed window open. On restart, the file had been overwritten.

Another possible and perhaps cleaner solution is to do the pretty print not into the existing buffer but into a new buffer not associated with a file, and leave the original buffer/file alone.

[GaryHughes]

A new buffer is a good idea, I'll experiment with that and see how it looks.