gddrescue, update mode?

[Petr Slansky]

Hello,

this is not a bug report but a request for new feature for gddrescue,
"update mode".
I use gddrescue a lot, to copy boot images to USB disks. I know I can use
old "dd" but I prefer gddrescue...

I miss a mode to update USB disk, it should work like this:

1) read block from destination disk
2) compare date from destination disk with source image
3) Are data the same? Then skip and continue go to step 1
4) otherwise do an update, write data from source disk to destination disk
and go to step 1

Advantages? Reads are faster than writes. USB disks have limited number of
writes they can accept (TBW parameter in SSD). I believe that "update mode"
can speed up some updates and lower number of blocks those have to be
written.

With regards,
Petr