Document all available flags in all of the subcommand synopsis texts.
diff --git a/git-flow-init b/git-flow-init
index d533934..ffc9e96 100644
--- a/git-flow-init
+++ b/git-flow-init
@@ -13,7 +13,7 @@
 #
 
 usage() {
-	echo "usage: git flow init"
+	echo "usage: git flow init [-f]"
 }
 
 parse_args() {