Shell names are not escaped!

[jfly]

Check this out:

$ shtuff as /foo
Traceback (most recent call last):
  File "/home/jeremy/.local/bin/shtuff", line 8, in <module>
    sys.exit(main())
  File "/home/jeremy/.local/lib/python3.9/site-packages/shtuff.py", line 83, in main
    func(**args)
  File "/home/jeremy/.local/lib/python3.9/site-packages/shtuff.py", line 93, in shtuff_as
    with open(pid_file, 'w') as f:
PermissionError: [Errno 13] Permission denied: '/foo.pid'

Note how it's trying to create a foo.pid directory at the root of my filesystem. That shouldn't happen!

The problem is that we don't do any escaping of the filename when calling get_pid_file:

$ python
>>> import shtuff
>>> shtuff.get_pid_file(name="/foo")
'/foo.pid'

vs:

>>> shtuff.get_pid_file(name="foo")
'/home/jeremy/.local/share/shtuff/foo.pid'

I think the fix is to have get_pid_file do some escaping of the name. The simplest option may be base64 encode the whole thing? Looking through https://stackoverflow.com/questions/295135/turn-a-string-into-a-valid-filename, https://stackoverflow.com/a/295150 mentions this, and warns to be careful to avoid the / character.