diff - display what has changed since last commit

To display everything that has changed, use git diff:

$ git diff
diff --git a/README b/README
index 2b7013e..4daf890 100644
--- a/README
+++ b/README
@@ -1,3 +1,5 @@
+(Why does nobody ever read README?)
+
 We are writing a book about Perl 6.

 It will be some kind of example-driven introduction to Perl 6, and at
$