Stackoverflow question 21693582

asdf@jkl:~/tmp$ ls
foo bar.md  foo.md  Makefile

asdf@jkl:~/tmp$ cat Makefile
# define a space
space:=
space+=

.SECONDEXPANSION:
%.html: $$(subst $$(space),\$$(space),%).md
	pandoc "$<" -o "$@"

asdf@jkl:~/tmp$ # verify it works when no spaces
asdf@jkl:~/tmp$ make foo.html
pandoc "foo.md" -o "foo.html"

asdf@jkl:~/tmp$ # now verify on spaces
asdf@jkl:~/tmp$ make foo\ bar.html
pandoc "foo bar.md" -o "foo bar.html"