1 Test if the file is read-only in rm.py;
2 ask the user if they wants to delete it.
5 Add option -f for rm.py.
8 Add option -s for cmp.py.
11 Extend remove-old-files.py: add option -v/--verbose to report every removed file.
14 Rename remove-old-files.py to find.py. Make options more GNU find-like.
17 Extend find.py: add options to find files by name, extension, path.
20 After dropping Python 2.7: use shutil.which().