mq: Document that qdel requires exact patch identifiers

hgext/mq.py

@@ -1851,8 +1851,9 b' class queue(object):'
 def delete(ui, repo, *patches, **opts):
     """remove patches from queue
 
-    The patches must not be applied, and at least one patch is required. With
-    -k/--keep, the patch files are preserved in the patch directory.
+    The patches must not be applied, and at least one patch is required. Exact
+    patch identifiers must be given. With -k/--keep, the patch files are
+    preserved in the patch directory.
 
     To stop managing a patch and move it into permanent history,
     use the :hg:`qfinish` command."""