If the argument to make_file can act like a file, return it.
This is useful for code that calls command functions, but doesn't
want to send I/O through the filesystem.
SOURCES=$(wildcard *.[0-9].txt)
MAN=$(SOURCES:%.txt=%)
HTML=$(SOURCES:%.txt=%.html)
all: man
man: $(MAN)
html: $(HTML)
%: %.xml
xmlto man $*.xml
%.xml: %.txt
asciidoc -d manpage -b docbook $*.txt
%.html: %.txt
asciidoc -b html $*.txt
clean:
$(RM) $(MAN) $(MAN:%=%.xml) $(MAN:%=%.html)