cd31e113 switched to passing options as
keyword arguments, which always creates a new hash.

9e4ff29f removed a now-unnecessary call
to `dup`, since the options could no longer be accidentally mutated.

a55620f3 switched back to passing
options as a positional argument for Ruby < 2.7, but didn't restore the
call to `dup`, which meant that the same options hash was now passed
with every method call and mutations leaked from one call to another.