The handling of relative paths in SystemIOWindows was broken by changes for #4256.
Change SystemIOWindows.PrefixWithUNC to only prefix paths with `\\?\` when they can be prefixed; i.e., only prefix paths that are fully qualified and that don't contain relative path components like `.` or `..`. This way, relative paths passed to SystemIOWindows methods work correctly again. Also support network paths specified using forward slashes; e.g., `//example.com/share/foo.txt`.
Simplify SystemIOWindows.GetFullPath since Path.GetFullPath will honor `\\?\` prefixes and can replace forward slashes with backslashes, etc.
Copy and adapt source for Path.IsPathFullyQualified from https://github.com/dotnet/runtime, which is MIT licensed.
Add unit test for Duplicati.CommandLine.BackendTool to validate the fix.
This fixes#4632.
InvariantCulture is useful when comparing / sorting human language strings in a culturely correct way. It handles things like accented letters in a way that makes sense to humans (e.g., 'a' should be sorted next to 'á', rather than after 'z').
Ordinal looks just at the raw code points of the characters. As such, it is recommended for use in cases when comparing system strings (file paths, command line parameters, config settings, etc.). Since it doesn't need to use the culture specific sorting rules, this method can often be faster.
For more information, see https://stackoverflow.com/questions/492799/difference-between-invariantculture-and-ordinal-string-comparison (and other related questions)
Added a current pointer-file to allow running with a version that is not the newest.
Updater is now working except for OSX, where the bundle setup is causing issues when running the loaded instance.
Kenneth Skovhede