pass fork option to copy from

Author: chm-diederichs

lib/core.js

@@ -224,7 +224,7 @@ module.exports = class Core {
     return false
   }
 
-  async copyFrom (src, signature, { length = src.tree.length, additional = [] } = {}) {
+  async copyFrom (src, signature, { length = src.tree.length, fork = src.tree.fork, additional = [] } = {}) {
     await this._mutex.lock()
 
     try {
@@ -334,7 +334,7 @@ module.exports = class Core {
 
       await batch.commit()
 
-      this.tree.fork = src.tree.fork
+      this.tree.fork = fork
 
       this.header.tree.length = this.tree.length
       this.header.tree.rootHash = this.tree.hash()