Expose server build information

Co-authored-by: Professor Bloodstone <git@bloodstone.dev>
Co-authored-by: Mark Vainomaa <mikroskeem@mikroskeem.eu>
Co-authored-by: masmc05 <masmc05@gmail.com>
Co-authored-by: Riley Park <rileysebastianpark@gmail.com>

paper-api/src/main/java/io/papermc/paper/util/JarManifests.java

@@ -0,0 +1,38 @@
+package io.papermc.paper.util;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
+import java.util.Collections;
+import java.util.Map;
+import java.util.WeakHashMap;
+import java.util.jar.Manifest;
+import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
+@NullMarked
+@ApiStatus.Internal
+public final class JarManifests {
+    private JarManifests() {
+    }
+
+    private static final Map<ClassLoader, Manifest> MANIFESTS = Collections.synchronizedMap(new WeakHashMap<>());
+
+    public static @Nullable Manifest manifest(final Class<?> clazz) {
+        return MANIFESTS.computeIfAbsent(clazz.getClassLoader(), classLoader -> {
+            final String classLocation = "/" + clazz.getName().replace(".", "/") + ".class";
+            final URL resource = clazz.getResource(classLocation);
+            if (resource == null) {
+                return null;
+            }
+            final String classFilePath = resource.toString().replace("\\", "/");
+            final String archivePath = classFilePath.substring(0, classFilePath.length() - classLocation.length());
+            try (final InputStream stream = new URL(archivePath + "/META-INF/MANIFEST.MF").openStream()) {
+                return new Manifest(stream);
+            } catch (final IOException ex) {
+                return null;
+            }
+        });
+    }
+}