[MacPorts] #18602: Prevent MacPorts from being configured with --prefix=/usr/local

[Rainer Müller]

MacPorts wrote:
> #18602: Prevent MacPorts from being configured with --prefix=/usr/local
> -------------------------------------+--------------------------------------
>  Reporter:  ryandesign@…             |       Owner:  macports-tickets@…                   
>      Type:  defect                   |      Status:  new                                  
>  Priority:  Normal                   |   Milestone:  MacPorts 1.8.0                       
> Component:  base                     |     Version:  1.7.0                                
>  Keywords:                           |        Port:                                       
> -------------------------------------+--------------------------------------
>  MacPorts should not allow users to configure it with
>  `--prefix=/usr/local`. Doing so surely breaks some ports, such as
>  [comment:ticket:15778:3 macfuse].

I don't think we should forbid it completely. Adding a warning and a
link to the appropriate FAQ entry should be enough.

The port macfuse is broken in a very different way, it's not respecting
${prefix} at all, but hardcoding /opt/local. The problem in the proposed
patch is that it is making assumptions about paths which it should not
be doing.

Imagine it would be untaring to ${destpath}/opt/local by default, there
would be the same problem just with another path. And I am pretty sure
you don't want to forbid that path being used as a prefix. Forbidding
paths being used as prefix is not the proper solution to fix the macfuse
port.

The problem can be overcome by comparing "/usr/local" to the current
prefix, rename it to a temporary filename before renaming to the real
target or untar only parts of the tarball to the correct location right
away.

This would work:
tar -xjf $tarname -C ${destpath}${prefix} --strip-components 2 usr/local
tar -xjf $tarname -C ${destpath} Library

Rainer