+# atomically create file by command
+cmdsave = @echo '$1' $2 \>$@; mispipe '$1 $2' 'ifne sponge $@'
+# download git checkout
+gitsave = @if cd $@ 2>/dev/null; \
+ then echo git pull $@; git pull -q --ff-only || true; \
+ else echo git clone $1 $@; git clone -q --progress $1 $@; fi
+