only read the history file if we have no history

git-svn-id: file:///home/svn/framework3/trunk@10117 4d416f70-5f16-0410-b530-b9f4589650da

lib/rex/ui/text/shell.rb

@@ -52,7 +52,7 @@ module Shell
 	def init_tab_complete
 		if (self.input and self.input.supports_readline)
 			self.input = Input::Readline.new(lambda { |str| tab_complete(str) })
-			if histfile and File.exists?(histfile)
+			if Readline::HISTORY.length == 0 and histfile and File.exists?(histfile)
 				File.readlines(histfile).each { |e| 
 					Readline::HISTORY << e.chomp 
 				}