Enable stdin piping

Author: santuchoagus

widip/watch.py

@@ -75,6 +75,7 @@ def widish_main(file_name, *shell_program_args: str):
     diagram_draw(path, fd)
     constants = tuple(x.name for x in fd.dom)
     runner = SHELL_RUNNER(fd)(*constants)
-    # TODO pass stdin
-    run_res = runner and runner("")
+
+    run_res = runner("") if sys.stdin.isatty() else runner(sys.stdin.read())
+
     print(*(tuple(x.rstrip() for x in tuplify(untuplify(run_res)) if x)), sep="\n")