Provide a place for commands to store state.

Commands can store state on an  `OpenStruct` exposed via the `state` method.
This `OpenStruct` is guaranteed to be unique to the command and to the associated Pry instance.

e.g

create_command "my-test" do
  def process
    state.my_state ||= 0
    state.my_state += 1
  end
end

The above `state.my_state` variable will increment by one for each invocation of `my-test`.
Further, it will not intefere with any state on `my-test` for any other Pry instance or with
any `state.my_state` variables defined for other commands on the same Pry instance.

lib/pry/command.rb

@@ -225,9 +225,20 @@ class Pry
       self._pry_        = context[:pry_instance]
     end
 
-    # The value of {self} inside the {target} binding.
+    # @return [Object] The value of `self` inside the `target` binding.
     def target_self; target.eval('self'); end
 
+    # @return [Hash] Pry commands can store arbitrary state
+    #   here. This state persists between subsequent command invocations.
+    #   All state saved here is unique to the command, it does not
+    #   need to be namespaced.
+    # @example
+    #   state.my_state = "my state"  # this will not conflict with any
+    #                                # `state.my_state` used in another command.
+    def state
+      _pry_.command_state[match] ||= OpenStruct.new
+    end
+
     # Revaluate the string (str) and perform interpolation.
     # @param [String] str The string to reevaluate with interpolation.
     #

lib/pry/pry_instance.rb

@@ -28,6 +28,9 @@ class Pry
 
   attr_accessor :extra_sticky_locals
 
+  # This is exposed via Pry::Command#state.
+  attr_reader :command_state
+
   # Special treatment for hooks as we want to alert people of the
   # changed API
   attr_reader :hooks
@@ -59,6 +62,7 @@ class Pry
 
     @binding_stack     = []
     @indent            = Pry::Indent.new
+    @command_state     = {}
   end
 
   # Refresh the Pry instance settings from the Pry class.

test/test_command.rb

@@ -623,4 +623,74 @@ describe "Pry::Command" do
        mock_pry("show-command my-test").should =~ /output.puts command_name/
      end
    end
+
+   describe "commands can save state" do
+     before do
+       @set = Pry::CommandSet.new do
+         create_command "litella", "desc" do
+           def process
+             state.my_state ||= 0
+             state.my_state += 1
+           end
+         end
+
+         create_command "sanders", "desc" do
+           def process
+             state.my_state = "wood"
+           end
+         end
+
+         create_command /[Hh]ello-world/, "desc" do
+           def process
+             state.my_state ||= 0
+             state.my_state += 2
+           end
+         end
+
+       end.import Pry::Commands
+     end
+
+     it 'should save state for the command on the Pry#command_state hash' do
+       instance = nil
+       redirect_pry_io(InputTester.new("litella",
+                                       "exit-all")) do
+         instance = Pry.new(:commands => @set)
+         instance.repl
+       end
+
+       instance.command_state["litella"].my_state.should == 1
+     end
+
+     it 'should ensure state is maintained between multiple invocations of command' do
+       instance = nil
+       redirect_pry_io(InputTester.new("litella", "litella",
+                                       "exit-all")) do
+         instance = Pry.new(:commands => @set)
+         instance.repl
+       end
+
+       instance.command_state["litella"].my_state.should == 2
+     end
+
+     it 'should ensure state with same name stored stored seperately for each command' do
+       instance = nil
+       redirect_pry_io(InputTester.new("litella", "sanders", "exit-all")) do
+         instance = Pry.new(:commands => @set)
+         instance.repl
+       end
+
+       instance.command_state["litella"].my_state.should == 1
+       instance.command_state["sanders"].my_state.should =="wood"
+     end
+
+     it 'should ensure state can is properly saved for regex commands' do
+       instance = nil
+       redirect_pry_io(InputTester.new("hello-world", "Hello-world", "exit-all")) do
+         instance = Pry.new(:commands => @set)
+         instance.repl
+       end
+
+       instance.command_state[/[Hh]ello-world/].my_state.should == 4
+     end
+   end
  end