feat: add cross-platform release pipeline [CI SKIP]

ci/Monitor.Tar/Program.cs

@@ -0,0 +1,38 @@
+using System.Formats.Tar;
+using System.IO.Compression;
+
+if (args.Length < 3)
+{
+    Console.Error.WriteLine("usage: Monitor.Tar <source-directory> <archive-path> <executable-relative-path>...");
+    return 2;
+}
+
+string sourceDirectory = Path.GetFullPath(args[0]);
+string archivePath = Path.GetFullPath(args[1]);
+HashSet<string> executables = args.Skip(2).Select(path => path.Replace('\\', '/')).ToHashSet(StringComparer.Ordinal);
+UnixFileMode executableMode = UnixFileMode.UserRead | UnixFileMode.UserWrite | UnixFileMode.UserExecute |
+                              UnixFileMode.GroupRead | UnixFileMode.GroupExecute |
+                              UnixFileMode.OtherRead | UnixFileMode.OtherExecute;
+UnixFileMode regularMode = UnixFileMode.UserRead | UnixFileMode.UserWrite |
+                           UnixFileMode.GroupRead | UnixFileMode.OtherRead;
+
+Directory.CreateDirectory(Path.GetDirectoryName(archivePath)!);
+using FileStream fileStream = File.Create(archivePath);
+using GZipStream gzipStream = new(fileStream, CompressionLevel.Optimal, leaveOpen: true);
+using TarWriter writer = new(gzipStream, TarEntryFormat.Pax, leaveOpen: true);
+
+foreach (string filePath in Directory.EnumerateFiles(sourceDirectory, "*", SearchOption.AllDirectories))
+{
+    string relativePath = Path.GetRelativePath(sourceDirectory, filePath).Replace('\\', '/');
+    PaxTarEntry entry = new(TarEntryType.RegularFile, relativePath)
+    {
+        Mode = executables.Contains(relativePath) ? executableMode : regularMode,
+        DataStream = File.OpenRead(filePath)
+    };
+    using (entry.DataStream)
+    {
+        writer.WriteEntry(entry);
+    }
+}
+
+return 0;