diff -r a20f5088013a -r 6e91fba485fa mercurial/commands.py
--- a/mercurial/commands.py	Fri Sep 16 14:37:56 2011 -0500
+++ b/mercurial/commands.py	Fri Sep 16 14:37:57 2011 -0500
@@ -3381,6 +3381,12 @@
        its first parent. Also, only files different from BOTH parents
        will appear in files:.
 
+    .. note::
+       for performance reasons, log FILE may omit duplicate changes
+       made on branches and will not show deletions. To see all
+       changes including duplicates and deletions, use the --removed
+       switch.
+
     .. container:: verbose
 
       Some examples: