You are in an area where pkgsrc is a bit weak.  However the
fundamentals of safe small operations are very strong.

I have two bits of advice:

  Don't try to mix pkgsrc-head and pkgsrc-stable.   It might make
  sense to have two package trees installed, but that seems hard.

  Use some mechanism to build the new package before tearing down the
  old ones.

The second bit should be more automated.  I'd recommend using pkg_comp
and then pkg_chk within the chroot, using -r to remove all mismatched
packages, and then -a to build back to your config file.  Then when
all is built you can binary update in the running system.




-- 
        Greg Troxel <gdt@ir.bbn.com>