dmg packages

[Craig Treleaven]

Hi:

I'm a bit confused about MacPorts packaging targets:  mpkg, dmg, etc. 
I don't have a spare system to test these things out.  I've looked at 
the documentation 
(http://guide.macports.org/#using.binaries.binary-packages) and the 
man page for port without enlightenment.

So, if I create a dmg of my port and a user installs it on another 
machine, I presume all the bits and bobs end up in the same file 
system locations as when I do 'sudo port install myport' on a machine 
with MacPorts.  IOW, virtually everything under ${prefix}.  Although 
${prefix} _must_ be /opt/local for a dmg install, no?

What happens if the destination machine has MacPorts installed before 
doing a dmg install?  Is "myport" now shown as an installed port? 
Can myport be deactivated by MacPorts?

If MacPorts is installed before doing an install with a dmg, what 
happens to dependencies that may already be present on the 
destination machine?  Ie the destination machine might have older, 
newer or the same version of one or more dependencies, possibily with 
different variants.  Does the dmg overwrite them?  Will the dmg warn 
about this?

What happens if MacPorts is installed _after_ the dmg install of 
myport?  Again, will Macports identify that myport and all its 
dependencies are installed?  Will 'sudo port upgrade' work?

What if the user wants to install an additional port that depends on 
myport (call it "myportplus").  If myport was installed via dmg and 
the user wants to install myportplus via MacPorts, will it be 
recognised that the myport dependency is already satisfied or will it 
be downloaded and installed fresh?  (Which many take multiple hours 
in my case as I depend on a non-default variant of Qt4-mac.)

Thanks for any light you can shed!

Craig