root:
             product   file:plan.py
             product   step:./plan.py

file:plan.py
               state = CONFIRMED
             creator   root:
                sink   step:./plan.py

step:./plan.py
               state = SUCCEEDED
                need = PLAN
           using_env = STEPUP_PATH_FILTER [dynamic]
           explained = yes
             creator   root:
              source   file:plan.py
             product   step:cp -p foo.txt bar.txt
             product   step:echo test > foo.txt

step:cp -p foo.txt bar.txt
               state = SUCCEEDED
                need = DEFAULT
           explained = yes
             creator   step:./plan.py
              source   file:foo.txt
             product   file:bar.txt
                sink   file:bar.txt

file:foo.txt
               state = BUILT
             creator   step:echo test > foo.txt
              source   step:echo test > foo.txt
                sink   step:cp -p foo.txt bar.txt

file:bar.txt
               state = BUILT
             creator   step:cp -p foo.txt bar.txt
              source   step:cp -p foo.txt bar.txt

step:echo test > foo.txt
               state = SUCCEEDED
                need = DEFAULT
           explained = yes
             creator   step:./plan.py
             product   file:foo.txt
                sink   file:foo.txt
