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 original.txt copy.txt
             product   step:echo 2 > original.txt

file:original.txt
               state = BUILT
             creator   step:echo 2 > original.txt
              source   step:echo 2 > original.txt
                sink   step:cp -p original.txt copy.txt

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

file:copy.txt
               state = BUILT
             creator   step:cp -p original.txt copy.txt
              source   step:cp -p original.txt copy.txt

step:echo 2 > original.txt
               state = SUCCEEDED
                need = DEFAULT
           explained = yes
             creator   step:./plan.py
             product   file:original.txt
                sink   file:original.txt
