last_rev := $(wildcard */.bzr/branch/last-revision)
html := $(patsubst %/.bzr/branch/last-revision,%/index.html,$(last_rev))

all: $(html)
.PHONY: all

%/index.html: %/.bzr/branch/last-revision %/Makefile
	flock -n "$*" $(MAKE) -C "$*" RST2HTML=rst2html
%/Makefile: bzr2html/.bzr/branch/last-revision
	bzr export -d ./bzr2html --format=tar - | flock -n "$*" tar -x -C "$*"