rust/hg-cpython/rustfmt.toml

rust: error for WdirUnsupported with cpython conversion as exception

This introduces WorkingDirectoryUnsupported as an enum variant
of GraphError in the core and converts it to the expected
`mercurial.error.WdirUnsupported`.

max_width = 79
wrap_comments = true
error_on_line_overflow = true