rule echo
command = echo $in
# Needed so we can run the original ninja on this file.
build b.txt c.txt d.txt m.txt expand$ this.txt expand$ this.png: phony
build x.txt: echo b.txt | c.txt
build y.txt: echo b.txt | c.txt d.txt
build z.txt: echo b.txt m.txt | c.txt d.txt
build w.txt: echo b.txt $foo.txt | $foo.png d.txt
foo = expand this
# No non-implicit inputs. Allowed.
build gla: echo | b.txt
# just a pipe. Also allowed.
build glab: echo |