Arch Linux pacstrap options

When creating a base Arch Linux image from scratch for Docker I found the documentation for pacstrap to be limited.
Pacstrap is installed as part of the arch-install-scripts and I eventually found the following options running as the root user

# pacstrap -h
usage: pacstrap [options] root [packages...]

  Options:
    -C config      Use an alternate config file for pacman
    -c             Use the package cache on the host, rather than the target
    -d             Allow installation to a non-mountpoint directory
    -G             Avoid copying the host's pacman keyring to the target
    -i             Avoid auto-confirmation of package selections
    -M             Avoid copying the host's mirrorlist to the target

    -h             Print this help message

pacstrap installs packages to the specified new root directory. If no packages
are given, pacstrap defaults to the "base" group.

The docker script I used was :

spawn pacstrap -C $PACMAN_CONF -c -d -G -i $ROOTFS base haveged 

$PACMAN_EXTRA_PKGS --ignore $PKGIGNORE