fsmgr != command -v fsmgr
ifeq ($(fsmgr),)
$(error "no fsmgr")
endif
UID != id -u
SUDO != [ 0 = "$(UID)" ] || echo sudo

.DEFAULT_GOAL = all

.PHONY: all clean cleaner
all: $(addprefix _filesystem/samizdat., seed.btrfs patch.btrfs)

subvolumes = _build _filesystem
$(subvolumes):
	$(SUDO) btrfs subvolume create $@

clean:
	-$(SUDO) btrfs subvolume delete _build
destroy: clean
	-$(SUDO) btrfs subvolume delete _filesystem

%.btrfs: | $(subvolumes)
	$(SUDO) $(fsmgr) build $@