Match docker cp entry naming and compression for tar streams

The stream copyOut path reused archiveDirectory for directories, which emits a
leading "./" and names entries relative to the directory itself, and always
compressed with gzip. Docker and podman name entries relative to the source's
parent, so the source's own basename is the top level entry, and emit an
uncompressed tar.

The difference is visible in a round trip: with contents-relative naming,
`cp ctr:/dir - | cp - other:/dest` scatters dir's children into /dest instead
of producing /dest/dir. The gzip framing also breaks consumers that read the
stream with a plain tar reader rather than shelling out to tar.

Use the parent-relative form for both files and directories whenever
request.isArchive marks the stream path, with no compression filter. The
internal directory copyOut, where isArchive is derived from the path being a
directory, keeps shipping pax+gzip of the directory's contents, which is what
the host side extracts into the destination directory.

Author: yash-mandaviya

vminitd/Sources/VminitdCore/Server+GRPC.swift

@@ -597,17 +597,21 @@ extension Initd: Com_Apple_Containerization_Sandbox_V3_SandboxContext.SimpleServ
             defer { try? sock.close() }
 
             if isArchive {
-                let fileURL = URL(fileURLWithPath: path)
-                let writer = try ArchiveWriter(configuration: .init(format: .pax, filter: .gzip))
+                // `request.isArchive` marks the `docker cp CONTAINER:/path -`
+                // stream path. Docker emits an uncompressed tar whose entries are
+                // named relative to the source's parent, so the source's own
+                // basename is the top level entry, for both files and directories.
+                // The internal directory copyOut instead ships pax+gzip of the
+                // directory's contents, which is what the host extracts into the
+                // destination directory.
+                let filter: Filter = request.isArchive ? Filter.none : Filter.gzip
+                let writer = try ArchiveWriter(configuration: .init(format: .pax, filter: filter))
                 try writer.open(fileDescriptor: sock.fileDescriptor)
-                if isDirectory.boolValue {
-                    try writer.archiveDirectory(fileURL)
-                } else {
-                    // Forced single-file archive: emit one entry named after the
-                    // file's basename, relative to its parent directory.
+                if request.isArchive {
                     let filePath = FilePath(path)
-                    let base = filePath.removingLastComponent()
-                    try writer.archive([filePath], base: base)
+                    try writer.archive([filePath], base: filePath.removingLastComponent())
+                } else {
+                    try writer.archiveDirectory(URL(fileURLWithPath: path))
                 }
                 try writer.finishEncoding()
             } else {