mq: document possible combination of -e and -n for qimport

mq: document possible combination of -e and -n for qimport

--- a/hgext/mq.py	Wed Jul 21 11:53:09 2010 +0900
+++ b/hgext/mq.py	Fri Jul 23 23:43:43 2010 +0900
@@ -1817,6 +1817,11 @@
     To import a patch from standard input, pass - as the patch file.
     When importing from standard input, a patch name must be specified
     using the --name flag.
+
+    You can import a patch existing inside the patch repository and
+    rename it on the go::
+
+      hg qimport -e existing-patch -n new-name
     """
     q = repo.mq
     try: