Option to allow saving backup files with date of last mod, instead of date of save

[mapazarr]

Hi, I would like to save my backup files using the date of the last modification of the file, instead of with the date of when the save was performed.

In shell terminology, basically the idea would be to copy the file using cp -a instead of just cp.

Eventually the date encoded in the name of the file should also be changed to the date of the last modification of the file.

This could be added as an option to the configuration settings, instead of as the default behavior.