When an InRelease file changes, apt-get update gives the following error:

E: Repository 'http://approx.local:9999/debian buster InRelease' changed its 'Suite' value from 'testing' to 'stable'
N: This must be accepted explicitly before updates for this repository can be applied. See apt-secure(8) manpage for details.

The apt-secure man page describes _why_ this happens, but gives
absolutely no clue about how to fix it.  While different front ends may
have different ways to do this, the apt-secure man page should at the
very least point explicitly to the --allow-releaseinfo-change option of
the apt-get man page, so the user can follow the error message to a
solution, without resorting to guessing or googling.