[[JENKINS-16301] Use a buffered input stream to get somewhat better performance also from Maven archiving.

Introducing Util.getDigestOf(File) as a convenience.

core/src/main/java/hudson/Util.java

@@ -588,6 +588,22 @@ public class Util {
         }
     }
 
+    /**
+     * Computes the MD5 digest of a file.
+     * @param file a file
+     * @return a 32-character string
+     * @throws IOException in case reading fails
+     * @since 1.525
+     */
+    public static String getDigestOf(File file) throws IOException {
+        InputStream is = new FileInputStream(file);
+        try {
+            return getDigestOf(new BufferedInputStream(is));
+        } finally {
+            is.close();
+        }
+    }
+
     /**
      * Converts a string into 128-bit AES key.
      * @since 1.308