No functional change is intended. The verbs where it wasn't immediately
clear if the success exit status is 0 or >= 0 are changed to explicitly
return 0. (I think it's better to be explicit than to rely on some call
stack always returning 0 on success.)
Some other functions are cleaned up to be more idiomatic.
Some of the functions so far were named do_xyz(), others dump_xyz() and
even others test_xyz(). let's instead name them exactly like the verb
exposed in the command line, just prefixed with verb_