pkg_add's upgrade option appears to run pkg_delete before its "Quick
pre-check if any conflicting dependencies are installed".

For example, if using it to install libxslt-1.1.5.tbz when libxml2-2.6.7
is installed (and libxml2>=2.6.8 is required), the pkg_delete is done
before (or irregardless to) that check.

(By the way, my enhanced pkg_add's upgrade option doesn't have that same
problem because it doesn't do any pkg_delete on the -u option. It uses -r
for the pkg_delete first and so that still has a problem then.)

   Jeremy C. Reed
   http://bsd.reedmedia.net/