[groff] Spooky action at a distance in line adjustment...sometimes

[G. Branden Robinson]

Hi all,

Something that increasingly puzzles me more as I try to learn about
groff is the fact that changes to a paragraph N can causes changes in
the way paragraph N+M's lines are adjusted, even if there are no textual
or other changes to paragraph N+M itself.

Can someone tells me why this happens?  And, more mysteriously, why it
only _sometimes_ happens?

Is this perhaps a bug?  Is some variable or register not getting
re-zeroed at paragraph breaks when it should be?  This may be a man
package-specific issue.

Screenshot attached.  I'm also attaching example diff output and the
patches to the sources of the files pictured.

-- 
Regards,
Branden

groff-line-adjustment-spooky-action-at-a-distance.png
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spooky.txt
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spooky.diff
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