Prompt what package to install when it is missing

[Jeremy Lavergne]

> That would answer the present question "what port provides this executable
> program in ${prefix}/bin" but what about ports like apache2 that install
> their binaries elsewhere?

If they're not in $PATH then we don't care.

> What about GUI programs? What about manpages or
> perl modules or php modules etc. that people sometimes ask about?

That's outside the scope of what we're trying to do here.

We're only after the programs people would like to execute from $PATH but
cannot be found.

> You talk of keeping a database of files, populated by the buildbot, I
> presume. What about ports the buildbot cannot build? What about
> differences in installed files based on variant or platform? Where would
> the database live -- on the server only, or copied to each user's
> computer? If on the server only, how does MacPorts query it? If on each
> user's computer, how is it synced?
>
> I also don't know how to change bash's behavior when a command is not
> found, but I guess that capability exists. How would we make this change
> for users? Currently the user's .profile is modified only by the installer
> package postflight script; how would users who selfupdate get this change?
> Do we take this opportunity to get away from inserting our code directly
> into .profile and switch to inserting just a command to source a script of
> our own, which I believe we already have in the repository but are not
> using yet?

I'd say simply mimic Ubuntu. We can then add further features later.

It'd be nice if we don't have to manipulate a user's shell script more
than adding the sourcing of a script somewhere; either way, if we stick to
something similar to other distributions (at least to start with) more
people will be familiar with the behavior.