virtual symlinks

["Jason R. Mastaler" <jason@xxxxxxxxxxxx>]

I am looking for a way to fool my shell into bypassing the correct
filesystem and adhering to the "fake" directory I choose when I access
that directory.

For example, when I "cd /usr/local" I want to really end up in
"/tmp/local" on the filesystem, but want my shell to think I am in 
/usr/local.  I need to do this because I have a ton of compiled source
trees which I need to install into a temporary directory instead of
it's target directory on the filesystem which is /usr/local for most.

For some, it will be as easy as copying into /tmp/local, but others
have already been configured with /usr/local as the target directory
and will be installed there when I do a "make install" or equivalent.
The number of source trees is so vast, I don't have time to
reconfigure them.  An equivalent way to accomplish this would be to
make a symbolic link from /usr/local --> /tmp/local, and then run the
installs, but I would like to be able to accomplish this without using
root priveleges and without interrupting a running system which this
symlink would do.

I hope this makes sense.  I am only subscribed to zsh-announce, so
please CC: me if you want to reply to the list.  I will post
a summary of results if desired.  Thanks.

Jason R. Mastaler                                 jason@xxxxxxxxxxxx