Every refusal the branching commands can emit now has a line a user can
read: the three size gates name the limit they hit with the number the
backend sent, the scope refusals (no branch of a branch, a released merge
base, a change kind an update cannot replay, a branch whose state moved)
each get their own message, and a Branching limits dialog reachable from
the panel footer states them before anybody meets one. The three numbers
come from ::get-branching-limits, so the copy keeps no second copy of a
limit it could drift from.
a6e7972297