- Don't test for '\\' in u3_unix_safe. Doing otherwise was crashing vere
when unmounting a mountpoint that had come to contain a file with '\\'
in its path. This might mean you can do bad things on Windows if other
checks fail.
- Ignore any files whose names do not pass `(sane %ta)` when scanning
directories. (This reimplements `(sane %ta)` in C. Perhaps it should
instead call `(sane %ta)`.)
- Use '~.' rather than '~' for the escape. We ignore files that end in
'~', probably for vim backup-file reasons.
- Add a _unix_string_to_knot missed in the prior conversion.
unix cannot represent the file with empty name, and it has special
mappings for '.' and '..'. as these three are all valid arvo `+knot`s,
we need to escape them if we come across them.
the method we use to escape is: if we encounter any of those three
`+knot`s, or any `+knot` starting with '~', we prepend its filename with
a '~'. and when going from filename to `+knot`, we do the reverse; i.e.
we ignore a '~' if it is the first character of a filename.
the current implementation just crashes if it encounters a `+knot`
containing '/' or '\\', neither of which are valid under the current
implementation of `@ta` (which only accepts numbers, lowercase, '-',
'~', '.', and '_'.)
it also crashes if it encounters a file containing '\\'. something else
should happen here; most likely vere should just ignore the file.
Fallback to the default happens in dawn.c, which correctly points to
roller.urbit.org, an endpoint that matches its request/response logic.
Continuing to use an Ethereum endpoint instead of an L2 one will just result
in 400s, since they don't speak the same language.
