Merge patch series "teach 'env default' to optionally keep runtime variables"

Rasmus Villemoes <ravi@prevas.dk> says:

Doing bringup of a board, part of my bootstrap logic is in U-Boot. So
when tweaking that logic, I was bitten by a previous completed
bootstrap having left a copy of the environment on the device, which
was imported and thus overrided the new logic.

So I thought, "ok, I'll just make sure to put 'env default -a' as the
first part of the bootstrap logic so I'm not bitten again". Alas, my
logic also relies on certain variables that are set by C code
(e.g. for detecting board variant), and doing 'env default -a' also
eliminates those.

Looking around, the hashtab code already supports a flag that does
exactly what I need, and exposing that is (morally) a one-liner.

Link: https://lore.kernel.org/r/20241030213404.2894247-1-ravi@prevas.dk