rdiff-backup: Restoring a file from its increments

[Dieter Heußner]

Hello,

could somebody shed some light to the question of restoring files backed up by 
rdiff-
backup, please?

Given an original file, say file A. It will be backed up with rdiff-backup, and 
also 
its increments (assuming that there are many changes to file A). 

When restoring a given version of that file,
a) does rdiff-backup construct the desired version step-wise by applying ALL 
increments of that file (in chronological order beginning with the original 
version), OR
b)  does rdiff-backup start with the original file (file A) and ONLY applies 
the most recent 
increment which relates immediately prior or precisely to the timestamp of the 
desired version to be restored?

In my understanding, if a) was true, deleting increments (say older than n 
weeks) would not always result in the desired version because of probably 
missing 
increments. If b) was true, the goal can be achieved. However, as a newbie to 
rdiff-backup 
I am not sure at all.
 
As a newbie to rdiff-backup I'd appreciate if the rdiff-backup documentation 
cover these issues for better understanding the mechanisms of this tool.

Best regards
Dieter 

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