I'd like to add DESTDIR support to pkg_add.  The idea would be that the
directory which is accessible as ${DESTDIR} at the time you run pkg_add
will later be the root directory (because you chroot to it, or because
you boot from a different disk, or move the disk to another system).

At present, you can sort of fake it with

    DESTDIR=/wherever
    PREFIX=/usr/pkg
    PKG_DBDIR=/var/db/pkg
    pkg_add -K ${DESTDIR}/${PKG_DBDIR} -p ${DESTDIR}/${PREFIX} pkgname.tgz

or, for syspkgs,

    DESTDIR=/wherever
    PREFIX=/
    PKG_DBDIR=/var/db/syspkg
    pkg_add -K ${DESTDIR}/${PKG_DBDIR} -p ${DESTDIR}/${PREFIX} pkgname.tgz

but the databases in ${DESTDIR}/${PKG_DBDIR}/*.db
end up with an unwanted "${DESTDIR}" as part of the file name.

I was thinking of adding a -D DESTDIR flag to pkg_add, so you could do

    DESTDIR=/wherever
    PREFIX=/usr/pkg
    PKG_DBDIR=/var/db/pkg
    pkg_add -D ${DESTDIR} -K ${PKG_DBDIR} -p ${PREFIX} pkgname.tgz

The following things would be interpreted relative to ${DESTDIR}:

    PKG_DBDIR
    PREFIX
    @cwd directories in the PLIST
    %D substitutions in the PLIST

I believe that FreeBSD's pkg_add has the ability to chroot, but I don't
want to do that, because (especially when installing syspkgs into a
previously empty directory) necessary tools might not exist in the
target directory.

Comments?

--apb (Alan Barrett)