msysPath function
Windows path path (C:\proj, C:/proj) in the form Git Bash and other
MSYS tools use (/c/proj), or null when it is not a drive path.
Implementation
String? msysPath(String path) {
final m = RegExp(r'^([A-Za-z]):([\\/].*)?$').firstMatch(path);
if (m == null) return null;
final rest = (m.group(2) ?? '').replaceAll(r'\', '/');
return p.posix.normalize('/${m.group(1)!.toLowerCase()}$rest');
}