Fixed problem with rolling back when there was a transaction running …

…on the main thread.

README.md

@@ -37,6 +37,14 @@ If one of your tasks ran in a transaction block and issued a rollback,
 parallelize will rollback all other threads, if they have rollback statements
 defined.
 
+Known Issues
+============
+
+Due to the threading you have to be sure to already have authenticated your SSH
+key (you're using SSH keys, right?) using an SSH agent before you run the
+parallelized code. Otherwise it'll blow up, let's just leave it at that. That'll
+change in the future.
+
 Installation
 ============
 

lib/capistrano/configuration/extensions/actions/invocation.rb

@@ -60,6 +60,7 @@ def wait_for(threads)
                 thread.join
               rescue
                 logger.important "Subthread failed: #{$!.message}"
+                thread[:exception_raised] = $!
               end
             end
           end

lib/capistrano/configuration/extensions/execution.rb

@@ -20,13 +20,22 @@ def current_task
           all_task_call_frames.last.task
         end
 
-        def transaction
+        def transaction?
+          !(rollback_requests.nil? && Thread.main[:rollback_requests].nil?)
+        end
+
+        def transaction(&blk)
           super do
             self.rollback_requests = [] unless transaction?
-            yield
+            blk.call
           end
         end
 
+        def on_rollback(&block)
+          self.rollback_requests ||= [] if transaction?
+          super
+        end
+
         def rollback!
           return if Thread.current[:rollback_requests].nil?
           Thread.current[:rolled_back] = true