diff -r 5d91f6e6f841 -r d1fe1a4eb2b7 mercurial/commands.py
--- a/mercurial/commands.py	Sat Feb 02 14:49:31 2008 +0100
+++ b/mercurial/commands.py	Sat Feb 02 14:55:14 2008 +0100
@@ -339,6 +339,8 @@
 
     Unless --force is specified, branch will not let you set a
     branch name that shadows an existing branch.
+
+    Use the command 'hg update' to switch to an existing branch.
     """
 
     if label:
@@ -358,6 +360,8 @@
     inactive.  If active is specified, only show active branches.
 
     A branch is considered active if it contains unmerged heads.
+
+    Use the command 'hg update' to switch to an existing branch.
     """
     b = repo.branchtags()
     heads = dict.fromkeys(repo.heads(), 1)