cookbook/container: example of building+running docker containers.

This got... long... and complicated.  But I think it's a really good
demonstration of getting redo to do complicated things elegantly.  At
least, I hope it is.

docs/cookbook/container/all.do

@@ -0,0 +1,88 @@
+exec >&2
+no_simple=
+no_debian=
+no_runlocal=
+no_runkvm=
+no_docker=
+
+if ! ./need.sh ldd; then
+	echo "skipping simple image."
+	no_simple=1
+fi
+if ! ./need.sh debootstrap eatmydata; then
+	echo "skipping debian image."
+	no_debian=1
+fi
+if ! ./need.sh fakeroot fakechroot ||
+   ! ./try_fakeroot.sh "x" true 2>/dev/null; then
+	echo "skipping chroot test."
+	no_runlocal=1
+	echo "skipping debian image."
+	no_debian=1
+fi
+if ! ./need.sh unshare ||
+   ! unshare -r true 2>/dev/null; then
+	echo " -- 'unshare -r' command doesn't work."
+	echo "skipping chroot test."
+	no_runlocal=1
+fi
+if ! ./need.sh busybox kvm; then
+	echo "skipping kvm test."
+	no_runkvm=1
+fi
+if ! ./need.sh docker ||
+   ! docker images >/dev/null; then
+	echo "skipping docker test."
+	no_docker=1
+fi
+if [ -n "$NO_SLOW_TESTS" ]; then
+	echo " -- NO_SLOW_TESTS is set."
+	echo "skipping debian image."
+	no_debian=1
+fi
+
+add() { targets="$targets $*"; }
+
+[ -z "$no_simple" ] && add simple.image.gz
+[ -z "$no_simple$no_runlocal" ] && add libs.runlocal
+[ -z "$no_simple$no_runkvm" ] && add libs.runkvm
+[ -z "$no_simple$no_docker" ] && add simple.rundocker
+
+[ -z "$no_debian" ] && add debian.image
+[ -z "$no_debian$no_runlocal" ] && add debian.runlocal
+[ -z "$no_debian$no_runkvm" ] && add debian.runkvm
+[ -z "$no_debian$no_docker" ] && add debian.rundocker
+
+redo-ifchange $targets
+
+check() {
+	label=$1
+	shift
+	printf "checking %-18s %-35s " "$label:" "$*" >&2
+	if test "$@"; then
+		printf "ok\n" >&2
+	else
+		printf "failed\n" >&2
+	fi
+}
+
+hellocheck() {
+	check "$1" "$(cat "$1")" = "Hello, world!"
+}
+
+debcheck() {
+	check "$1" "$(cat "$1")" -ge "70"
+	check "$1" "$(cat "$1")" -le "100"
+}
+
+if [ -z "$no_simple" ]; then
+	[ -n "$no_runlocal" ] || hellocheck libs.runlocal
+	[ -n "$no_runkvm" ] || hellocheck libs.runkvm
+	[ -n "$no_docker" ] || hellocheck simple.rundocker
+fi
+
+if [ -z "$no_debian" ]; then
+	[ -n "$no_runlocal" ] || debcheck debian.runlocal
+	[ -n "$no_runkvm" ] || debcheck debian.runkvm
+	[ -n "$no_docker" ] || debcheck debian.rundocker
+fi