Add comments to try to prevent recurrence of #31495.

There is a bad design choice in two of our configuration types,
where the empty string encodes a value that is not the same as the
default value.  This design choice, plus an implementation mistake,
meant that config_dup() did not preserve the value of routerset_t,
and thereby caused bug #31495.

This comment-only patch documents the two types with the problem,
and suggests that implementors try to avoid it in the future.

Closes ticket 31907.

0 files changed, 0 insertions, 0 deletions