Add --only, a more aggressive version of --excluded-packages

src/main/java/net/md_5/specialsource/JarRemapper.java

@@ -165,10 +165,14 @@ public class JarRemapper extends CustomRemapper {
         return mapped == null ? name : mapped;
     }
 
+    public void remapJar(Jar jar, File target) throws IOException {
+        remapJar(jar, target, Collections.EMPTY_SET);
+    }
+
     /**
      * Remap all the classes in a jar, writing a new jar to the target
      */
-    public void remapJar(Jar jar, File target) throws IOException {
+    public void remapJar(Jar jar, File target, Set<String> includes) throws IOException {
         if (jar == null) {
             return;
         }
@@ -185,7 +189,7 @@ public class JarRemapper extends CustomRemapper {
 
                 try (InputStream is = jar.getResource(name)) {
                     byte[] data;
-                    if (name.endsWith(".class")) {
+                    if (name.endsWith(".class") && shouldHandle(name, includes)) {
                         // remap classes
                         name = name.substring(0, name.length() - CLASS_LEN);
 
@@ -224,6 +228,23 @@ public class JarRemapper extends CustomRemapper {
         }
     }
 
+    private static boolean shouldHandle(String name, Set<String> includes) {
+        if (includes.isEmpty()) {
+            return true;
+        }
+
+        for (String match : includes) {
+            if (match.equals(".") && !name.contains("/")) {
+                return true;
+            }
+            if (name.startsWith(match)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
     /**
      * Remap an individual class given an InputStream to its bytecode
      */

src/main/java/net/md_5/specialsource/SpecialSource.java

@@ -34,6 +34,8 @@ import net.md_5.specialsource.provider.JointProvider;
 import net.md_5.specialsource.provider.JarProvider;
 import java.io.*;
 import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashSet;
 import java.util.List;
 import com.google.common.collect.BiMap;
 import com.google.common.collect.HashBiMap;
@@ -134,6 +136,10 @@ public class SpecialSource {
                 acceptsAll(asList("e", "excluded-packages"), "A comma seperated list of packages that should not be transformed, even if the srg specifies they should")
                         .withRequiredArg()
                         .ofType(String.class);
+
+                acceptsAll(asList("only"), "Process only the specified packages. Similar to --excluded-packages but applies at the processing rather than loading phase")
+                        .withRequiredArg()
+                        .ofType(String.class);
             }
         };
 
@@ -286,7 +292,7 @@ public class SpecialSource {
 
             log("Remapping final jar");
             JarRemapper jarRemapper = new JarRemapper(null, jarMapping, accessMapper);
-            jarRemapper.remapJar(jar3, (File) options.valueOf("out-jar"));
+            jarRemapper.remapJar(jar3, (File) options.valueOf("out-jar"), new HashSet<String>((Collection<String>) options.valuesOf("only")));
         }