A<digit><digit><whatever-else-you-want> is for --build target. It is executed
    before build starts; after unpacking the build system, and unpacking the
    source, and satisfying the build-dependency.

B<digit><digit><whatever-else-you-want> is executed after build system finishes
    building, successfully, before copying back the build result.

C<digit><digit><whatever-else-you-want> is executed after build failure,
    before cleanup.

D<digit><digit><whatever-else-you-want> is executed before unpacking the source
    inside the chroot, after setting up the chroot environment. Create
    $TMP, and $TMPDIR if necessary. This is called before build-dependency is
    satisfied. Also useful for calling apt-get update

E<digit><digit><whatever-else-you-want> is executed after pbuilder --update
    and  pbuilder --create finishes apt-get work with the chroot, before
    umounting kernel file systems (/proc) and creating the tarball from the
    chroot.

F<digit><digit><whatever-else-you-want> is executed just before user logs in, or
    program starts executing, after chroot is created in --login or --execute
    target.

G<digit><digit><whatever-else-you-want> is executed just after debootstrap
    finishes, and configuration is loaded, and pbuilder starts mounting
    /proc and invoking apt-get install in --create target.
