Only create a new backup when it differs from the previous backup

[joelpt]

Only create a new backup when it differs from the previous backup (or when a previous backup doesn't exist).

This will save disk space and improve the apparent functionality of the backup navigator. It will also make the backup_on_open_file option more useful by avoiding the creation of spurious backups.

[primitives]

Was this ever integrated into the plugin? I'm working with ST2 and it seems to create backups anytime a file is opened or selected / previewed in the project tree, so if you keep hitting up arrow / down arrow on 2 files over and over, it creates dozens of backups even though the file is only being previewed and not actually opened.

This is really the only thing missing from this plugin.