-re-> arrows now rename their parent directories (like -->) and don't require a
full match (like -exact->). Their old behaviour is available as -exact-re->.
Also, this change adds the ">>" arrow head, which modifies the current path and
continues to the next rule when it matches.
Previously, regex-matching paths on windows would, in some cases, require four
backslashes ('\\\\') to escape a single path separator. That's just too much.
With this commit, regex transforms now use '/' instead of '\' as path separator,
meaning rules can more easily be shared between platforms (although they are not
guaranteed to be 100% compatible since on Windows, '\' is still recognized as a
path separator).
To make rules more intuitive to write, local relative paths are now also printed
with '/' as path separator on Windows. Since Windows also accepts '/' as path
separator, this change doesn't really affect other rules that parse their sides
as paths.
Path should only be used when we need to access the file system. For all other
purposes (mainly crawling), we use PurePath instead since the paths don't
correspond to paths in the local file system.
