[gentoo-alt] minimal portage prefix install

[Timo Kluck]

Dear Gentoo-Alt developers,

I would like to use portage prefix for my own custom package tree,
independently from the standard portage tree and overlays. I found it
quite difficult to isolate the necessary steps for that from the
bootstrapping scripts.

For example, suppose that I have two packages, called package-a and
package-b. Suppose they have an automake file that just puts empty
files at $prefix/a and $prefix/b, respectively. So with gentoo-prefix,
I'm expecting those files to end up at $EPREFIX/usr.

(1) How would I install portage-prefix, preferably from git, to
$EPREFIX? Is just

    ./autogen.sh
    ./configure --prefix=$EPREFIX/usr --with-portage-user=$USER
--with-portage-group=$USER
    make
    make install

sufficient?
(2) How would I setup the configuration files for portage and the two
ebuilds on my local system?

So I'm trying to use the system's bash, make etc.

This is part of my effort to see whether we can use an existing,
well-maintained package manager to replace the current naive packaging
system of Sage (www.sagemath.org).

Thanks a lot in advance!
Timo Kluck