Tracking which ports were installed explicitly

[Ryan Schmidt]

Joshua proposed that we should track which ports were installed  
explicitly (via "sudo port install x") vs. which ports were installed  
via dependencies.

As he said in the ticket -- http://trac.macports.org/ticket/15260 :

> Keeping track of which ports the user explicitly asked to be  
> installed, as opposed to those installed only to fulfil  
> dependencies, would be quite useful. It would be analogous to  
> Gentoo's 'world'. With this information, we could do things like  
> uninstall all the ports that are no longer required after  
> uninstalling some other port.
>
> It shouldn't be hard to store the information by adding a magic  
> port name to the dep_map which depends on all the explicitly- 
> installed ports. We'd then need code to figure out during install  
> whether the port was explicitly asked for, and add the dep_map  
> entry. We'd also need to change the dependents check in uninstall  
> to not complain if the only dependent is the magic 'world' port.
>
>


Some discussion has taken place in the ticket and I'd like to move  
that discussion to this mailing list so we can get more input, and  
since it's easier to discuss things on the mailing list without  
cluttering up the ticket. Once we reach a consensus on what should be  
done, a summary can go into the ticket.


I mentioned the parallel with CPAN, which to my recollection has a  
feature where when you uninstall X, and if it depends on Y, and  
nothing else depends on Y, it will ask interactively if you want to  
uninstall Y as well. I pointed out that MacPorts has no interactivity  
at this time (except if you explicitly enter interactive mode by  
typing just "port"), and that I value this guarantee of non- 
interactivity.

Rainer and I liked the idea of a new pseudo-port (I called it  
"unused"; Rainer called it "orphaned" which is probably better) that  
you could use to deal with the ports that had been installed as  
dependencies of things which themselves have already been  
uninstalled. Then you could do the usual things like "port installed  
orphaned" or "sudo port uninstall orphaned".

The idea is to have MacPorts keep track of what you installed  
explicitly and what was installed automatically as a dependency. I  
think it might be of value to be able to manipulate this after the  
fact, both by changing something from an explicitly installed port to  
an automatically installed dependency (e.g. things that you would  
have let MacPorts install as a dependency except that you had to  
install it explicitly to get a particular variant) and by changing  
something from an automatically installed dependency to an explicitly  
installed port (e.g. things that you let MacPorts install as a  
dependency but which you want to keep around). Though I'm not  
convinced it's essential, and maybe it can be deferred until later  
anyway.

I also brought up the need to consider how this feature would affect  
the MacPorts framework/API. Probably a new pseudo-port wouldn't need  
any special changes in the API which would be good.

I'd like to solicit opinions on any and all of these matters, so let  
the discussion begin!