Added default implementation with warning for symbolic links

[RealOrko]

Hi

I changed the default implementation for writing symbolic links to emit a warning instead of throwing an exception for this issue.

Not sure how this runs for performance.

Another thing we could try is to create platform specific commands that call out to a shell command for the various platforms.

Something like:

if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux)) {
   ShellCommands.Exec($"mklink /H {source} {target}")
} else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX)) {
   ShellCommands.Exec($"ln -s {target} {source}")
} else if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows)) {
   ShellCommands.Exec($"ln -s {target} {source}")
}

[RealOrko]

After using this source code for launching OS specific shell commands, I did manage to unpack a tar with symbolic links using this code:

var opt = new ExtractionOptions {
    ExtractFullPath = true,
    Overwrite = true,
    WriteSymbolicLink = 
        (symbolicLink, actualPath) =>
        {
            if (Process.OperatingSystem.IsLinux() || Process.OperatingSystem.IsMacOS())
            {
                var symbolicLinkDirectory = Path.GetDirectoryName(symbolicLink);
                if (!Directory.Exists(symbolicLinkDirectory))
                {
                    Directory.CreateDirectory(symbolicLinkDirectory);
                }

                var result = new Process.Process()
                    .SetWorkingDirectory(symbolicLinkDirectory)
                    .SetEnvironmentVariable("PATH", Environment.GetEnvironmentVariable("PATH"))
                    .Execute("ln", "-s", actualPath, symbolicLink);

                if (result.HasErrorOutput())
                {
                    Console.WriteLine(result.ErrorOutput);
                }
            }
            else
            {
                Console.WriteLine($"Could not write symlink {symbolicLink} -> {actualPath}, for more information please see https://github.com/dotnet/runtime/issues/24271");
            }

        }
};

[adamhathcock]

Thanks for this. Should probably put some kind of warning in.