Three fixes, the first leading to the need to fix the second, and that
fix making dealing with the third be straightforward.
First, make the furthest level reached in any given branch be considered
interesting by #overview, even if no interesting features have been
encountered. This will result in listing Gnomish Mines and their first
level when someone goes down the stairs and immediately back up. It will
also produce a reminder of how far you've been--in each branch--after
retreating for any reason, without the need to manually add an annotation.
Second, #overview was suppressing the range of level numbers for Sokoban
because the author realized that the values were wrong. The record of
the furthest level reached was incorrect for builds-up branches, always
sticking with the deepest level even though it was the entrance. The
overview patch neglected to do the same suppression for Vlad's Tower and
the level range ("36 to 38" or similar) there was wrong. This fixes the
furthest level reached problem and also fixes #overview's level range
handling for builds-up branches.
Third and last, a long-standing issue which I don't think has ever been
formally reported: the level difficulty calculation used for monster
creation treated the upper (harder to get to) levels of builds-up branches
as if they were easier since they're closer to the surface as the gopher
burrows. So sokoban generated easier monsters on its final level than on
the ones leading up to that. Make depth for difficulty purposes account
for descent to the entrance and then ascent to the level of interest.
There was a distressing amount of trial and error involved. The dungeon
layout structures are not exactly easy to work with, and I never managed
to get builds_up() based on branch data to work correctly. Basing it on
dungeon data works as intended provided the branch has more than one
level, but it will yield incorrect result if we ever add a single-level
branch reached via stairs up rather than stairs down.
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