> > Wouldn't it be better to create a new way with
> > a fake id in the merge process?
>
> That would possibly create problems with through route relations and
> turn restrictions which reference the original way ids.

OK, understood.
>
> > I think that also would help debugging.
>
> I my opinion a fake id does not really help debugging because you don't
> have any reference. A good way would be to use the original id but an
> indicator that the way has been modified.

The problem that I see is that we write messages to the log
containing the way ids. This can be very confusing when the
way is not nearly identical to the way in the input file, esp.
if the log message relates to points of a different way that was
merged into the stated way.
Maybe you can create a tag  like mkgmap:road-merge-info
that contains the merged ids? That would at least allow
to modify StyledConverter.getDebugName() to use that info.

Gerd