I am trying to find documentation on the suggested steps for upgrading a
compatible library via pkgsrc and using packages.

This is a posting I read:

 In debian, if libpng2 gets a fix, a new rev of libpng2 goes in "in
 place". In pkgsrc, the only way to replace libpng2 would be to uninstall
 everything that depends on it, then replace it, then reinstall everything
 on top.  Arguably correct in an impractical sort of way...

Is "pkg_add -u" the correct way for updating a compatible library
using a package?

What are the steps (or variables to set) so "make update" does not first 
deinstall all depending packages?

Is there any code that first compares the dependencies' DEPENDS so it will
only deinstall if there is truly a conflict?

Of course, this doesn't just apply to libraries.

Thanks,

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