> desired result.  a little user education is what is really needed.
                        ^^^^^^^^^^^^^^^^^^^^^
   Or a little change to a makefile or two?

little?  one or two?  you're moving the entire src/include directory
around, not making a little change.
   
   > i can't feel sorry for people compiling the full netbsd tree who
   > aren't at least aware of the issues involved -- it is just too big.
                                  ^^^^^^^^^^^^^^^
   I, for one, can't tell *why* include files have changed, so I have no idea
   what to rebuild. I would prefer to let the makefiles do this for me, but

this is what "make depend" is for.  i let it decide what must change
and what must not.

   I don't think that the '${MAKE} cleandir' in /usr/src/Makefile below the
   build: target is appropriate. I think the build: target should be rebuild:.
   
   > it is just too big.
   
   And to do a '${MAKE} cleandir' _just in case_ is not my idea of fun.

i use cleandir in specific dirs, but never on my source tree.  i just
make depend && make && make install.
   
   > i must admit that i had the same reaction to your original proposal
   > as chris did.
   
   Hmm. He didn't respond.

i mean the "how do you do this?".

   > .mrg.
   
   Thanks for the response, but do you even accept that there is a problem?

there is a problem.  i don't have a solution to it, but i'd rather things
stayed the way they are, than make the changes you suggested.

.mrg.