Cleanup and privatise commit comparator

src/main/kotlin/tinyvm/Object.kt

@@ -0,0 +1,17 @@
+package tinyvm
+
+import java.security.MessageDigest
+import java.util.HexFormat
+
+/**
+ * Represents an arbitrary version manager object.
+ */
+abstract class Object(val type: String) {
+    abstract val data: String
+
+    fun hash(): String =
+        HexFormat.of().formatHex(
+            MessageDigest.getInstance("SHA-1")
+                .digest("$type ${data.length}\u0000$data".toByteArray()),
+        )
+}