Hey, I'm trying to create a pipeline that takes files from a flat directory source/ that contains files with names formatted as yyyy-mm-dd-some-file-name.md and processes them with the output being created in destination/yyyy/mm/dd/some-file-name.md. I managed to string together an ugly script that converts the source path to destination path, but the problem is that make says that there is no rule to make the target. Here is my code so far:

SOURCE := $(wildcard source/*.md)
DESTINATION := $(foreach f,SOURCE,destination/$(shell echo $(notdir $(f)) | sed -E 's/^([0-9]{4})-([0-9]{2})-([0-9]{2})-(.*)\.md$$/\1\/\2\/\3\/\4.md/'))

$(DESTINATION): $(SOURCE)
	@mkdir -p $(dir $(shell echo $(notdir $@) | sed -E 's/^([0-9]{4})-([0-9]{2})-([0-9]{2})-(.*)\.md$$/\1\/\2\/\3/'))
	/bin/bash ./myscript.sh $< > $@

I believe that make sees that there are no target directories yet and just aborts the rule, but I'm not knowledgeable enough and just starting out with that tool. I would appreciate some guidance if any of you folks know a bit of Make.