* Order includes.
* Turn the diff type into an enum.
* Turn an unreachable error message into an assertion.
* Remove unused debugging code.
* Remove some dead assignments.
* Consistently use 1 instead of EXIT_FAILURE.
* Turn a return from main() into an exit().
MFC after: 1 week
Sponsored by: Klara, Inc.
Reviewed by: bapt
Differential Revision: https://reviews.freebsd.org/D55517
Dag-Erling Smørgrav
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