@stermeau
could you please provide sufficiently explanatory comments
directly in the code so that others who may at any time later
have to maintain that code can understand why that code is
as it is, cf. https://github.com/rear/rear/wiki/Coding-Style

FYI:
Fortunately for me personally it is no issue how code
for third-party backup tools is because I do not have
such tools so that I will never ever personally care about
that code (cf. #823).
But probably other users who use such tools may appreciate it
when they can maintain the existing code properly if needed.

@jsmeix I have added some comments. Is it what you had in mind?

@stermeau
many thanks for your added comments in the code.
At least for me it makes the code much easier to understand!