revisions for each source file, not backup runs

I would like to have a backup that keeps the last 5 revisions of each source file. This is not the same as last five incremental backup runs! I want the revision control applied at each source file, not for the backup run. The feature ‘revision_no_max’ applies to revisions of backup runs. How can I take revisions of each source file?

The need for revisions on each source file is obvious. Suppose, I set revision_no_max to 5. I edit file A five times with incremental backups between each edit. I end up with 5 backup files that have the last five versions of file A. Now I edit file B and when I make an incremental backup, I lose the backup file that has 5th oldest copy of file A. When we schedule backup for a directory with many files, this ‘one file’s revisions trumps another file’s revision’ effect will be amplified.