Fix issue progit#577: One command is git mv, instead of mv.

book/02-git-basics/sections/recording-changes.asc

@@ -595,5 +595,5 @@ $ git add README
 ----
 
 Git figures out that it's a rename implicitly, so it doesn't matter if you rename a file that way or with the `mv` command.
-The only real difference is that `mv` is one command instead of three – it's a convenience function.
+The only real difference is that `git mv` is one command instead of three – it's a convenience function.
 More importantly, you can use any tool you like to rename a file, and address the add/rm later, before you commit.