`CopyOnWriteLinkSupportedBetweenPaths` throws for a source on a mapped network drive

Start with WindowsCopyOnWriteFilesystem.cs, especially CopyOnWriteLinkSupportedBetweenPaths, and read VolumeInfoCache.cs around GetVolumeForPath. Reproduce the call with a file on a mapped Q: drive; done means the method returns false instead of throwing when no known volume exists.

The XML documentation of ICopyOnWriteFilesystem.CopyOnWriteLinkSupportedBetweenPaths says:

Determines whether a copy-on-write link can be created between the provided paths.

Returns: True if a link can be created, false if it cannot.

A mapped network drive does not support a link. The expected result is therefore false, not an exception. However, the method throws:

System.ArgumentException: No known volume information for 'Q:\share\big-installer.zip'. If the drive was added recently you may need to recreate the filesystem cache.
   at Microsoft.CopyOnWrite.Windows.VolumeInfoCache.GetVolumeForPath(String path) in D:\CoW\lib\Windows\VolumeInfoCache.cs:line 102
   at Microsoft.CopyOnWrite.Windows.WindowsCopyOnWriteFilesystem.CopyOnWriteLinkSupportedBetweenPaths(String source, String destination, Boolean pathsAreFullyResolved) in D:\CoW\lib\Windows\WindowsCopyOnWriteFilesystem.cs:line 46

Q: is a mapped network drive. VolumeInfoCache holds the local volumes only, so GetVolumeForPath finds no volume for the path and throws.

Steps to reproduce

1. Map a network share to a drive letter, for example Q:.
2. Put a file on that share.
3. Call CopyOnWriteLinkSupportedBetweenPaths with the file on Q: as the source.

Result: the call throws ArgumentException.
Expected: the call returns false.

Suggested fix

Return false for a path with no known volume, in the same way that the volume enumeration ignores a volume that gives an error. The release history shows this pattern for other volume errors:

• 0.3.7: ignore ACCESS_DENIED on volume enumeration.
• 0.3.9 to 0.3.12: ignore FILE_NOT_FOUND, ERROR_NO_SUCH_DEVICE, and
  ERROR_DEV_NOT_EXIST on volume enumeration.
• 0.4.2: ignore any volume that gives an error.

A mapped network drive is arguably the next case in this series.

Version

• CopyOnWrite 0.5.0 (NuGet)
• .NET 8, Windows 11