filename. Some commands (like "``tahoe cp``") use the lack of an alias to
mean that you want to refer to a local file, instead of something from the
Tahoe-LAFS filesystem. Another way to indicate this is to start the
-pathname with a dot, slash, or tilde.
+pathname with "./", "~/", "~username/", or "/".
When you're dealing a single starting directory, the ``tahoe:`` alias is
all you need. But when you want to refer to something that isn't yet