Go to some code file in Idea 13. Right click on it. Why "Git->Show history" and "Git->Show history for Selection" options are in grey using Git with Intellij Idea 13?
From settings->Version Control edit the "Directory" entry in the table on the right pane and replace "project" with your project root path. You should now be able to show the history of files.
(This is of course a workaround, I'm not sure what IntelliJ considers to be the "project" directory)