Avoiding install of x86_64 packages for i386 builds

[Jeff Sheltren]

I'm having a problem when building packages which have a dependency  
sitting in the plague 'repo_dir'.  Since plague puts all arches of a  
package in the same sub directory under 'repo_dir', if a package has  
both i386 and x86_64 binaries, later builds which pull in those  
packages as a dependency will install the x86_64 binary rather than  
the i386 one.  Yes, I have brought this problem on myself - I want to  
have stuff in repo_dir be usable for builds even before those  
packages are pushed to the main repository.  In order to do this, I  
have to point mock to the same repodir for both i386 and x86_64.

So, I have a couple of questions:  is there a way to have plague sort  
packages in the repo_dir differently than it does by default?  How  
does Extras avoid this problem?

Here's an example of the directory structure used:

---- Snip from /etc/mock/fedora-3-i386-core.cfg ---
[updates-plague]
name=updates-plague
baseurl=file:///build/plague/repodir/fedora-3-core/
---- End Snip ----

$ pwd
/build/plague/repodir/fedora-3-core
$ ls
mozilla   repodata
$ ls mozilla/1.7.13-1.3.1.legacy/
i386  SRPM  x86_64

Thanks,
Jeff