Symlink reparse points not resolved above the mount point

Bug Report

I think there is something loose in the code that solves symlinks.

• Relative paths crossing the mount point fail to work for both files and directories.
• Directory symlinks with relative paths pointing to the mount point (not only above it) will fail to be traversed by applications.

When testing with directories:

• cd from cmd: The name of the file cannot be resolved by the system.
• Windows Explorer shows a similar error when trying to open the symlink.
• WinFSP returns 0xC0000280 (STATUS_REPARSE_POINT_NOT_RESOLVED).

Absolute paths work OK. The symlinks that trigger this behavior work OK when moved down the file hierarchy.

How to Reproduce

Case 1 - Link to dot

C:\SOMEWHERE\MOUNT_POINT> mkdir dir
C:\SOMEWHERE\MOUNT_POINT> cd dir
C:\SOMEWHERE\MOUNT_POINT\dir> mklink /D link .
C:\SOMEWHERE\MOUNT_POINT\dir> cd link # You can also try to open it in Windows Explorer.
C:\SOMEWHERE\MOUNT_POINT\dir\link>
# This is OK. New path is ends with "link". Actually, we are in the same directory.

C:\SOMEWHERE\MOUNT_POINT\dir\link> cd ..
C:\SOMEWHERE\MOUNT_POINT\dir> move link ..
C:\SOMEWHERE\MOUNT_POINT\dir> cd ..
C:\SOMEWHERE\MOUNT_POINT> cd link # You can also try to open it in Windows Explorer.
The name of the file cannot be resolved by the system.
# [[ This is KO! ]]

Case 2 - Link to dot-dot

C:\SOMEWHERE\MOUNT_POINT\dir> mklink /D link ..\.. # Target is "C:\SOMEWHERE"
C:\SOMEWHERE\MOUNT_POINT\dir> cd link # You can also try to open it in Windows Explorer.
The name of the file cannot be resolved by the system.
# [[ This is KO! ]]

Behaviors

It would be expected to be able to access both, the mount point directory and locations out of it by using relative symlinks (already possible with absolute paths).

Environment

• OS version and build: 10.0.19044.2006
• WinFsp version and build: WinFsp 2022.2 Beta 1 (C# version of the library).