unset decommissioned nvram variables between releases

[wellloaded]

This is a "secondary" but rather important task when upgrading.
Often variables are dropped as not needed any more, it would be great to have a second script (even downloaded by ftup) to identify what variables are to be unset going from version X to version Y.

There was a thread on the forum long time ago about this topic, now with ftup we have the possibility to have this implemented while upgrading (e.g. just before the flashing is happening)

It is admittedly nice to have only, but it shouldn't be terribly difficult, and it's probably a longish git syntax to extract what we require, I'll see if I can post some ideas to spot them.

[HommeOursPorc]

FreshTomato-Project/freshtomato-arm#226

Also, @pedro0311 stating we pretty much reached the maximum image size for MIPS or some MIPS devices... This mean no ftup because my script is getting bigger by the day :-(

[wellloaded]

@HommeOursPorc can you please remind me if mtd-write returns an exit code after the flashing attempt?

[HommeOursPorc]

Yes it does. IIRC there is only one exit code, so no details, it only state if the flash was good or not.