diff -r d7e8baa28beb src/cmd/goinstall/doc.go
--- a/src/cmd/goinstall/doc.go	Sat Mar 19 15:09:39 2011 +0100
+++ b/src/cmd/goinstall/doc.go	Sat Mar 19 16:07:02 2011 +0100
@@ -14,6 +14,7 @@
 
 Flags and default settings:
         -a=false          install all previously installed packages
+	-clean=false      clean the package directory before installing
 	-dashboard=true   tally public packages on godashboard.appspot.com
 	-log=true         log installed packages to $GOROOT/goinstall.log for use by -a
 	-u=false          update already-downloaded packages