diff -r 8e46e59aaf4c -r 56380212d630 mercurial/commands.py
--- a/mercurial/commands.py	Mon Nov 03 16:30:21 2008 +0100
+++ b/mercurial/commands.py	Mon Nov 03 16:31:47 2008 +0100
@@ -1003,6 +1003,9 @@
     Without the -a option, diff will avoid generating diffs of files
     it detects as binary. With -a, diff will generate a diff anyway,
     probably with undesirable results.
+
+    Use the --git option to generate diffs in the git extended diff
+    format. Read the gitdiffs help topic for more information.
     """
     node1, node2 = cmdutil.revpair(repo, opts.get('rev'))
 
@@ -1036,6 +1039,9 @@
     it detects as binary. With -a, export will generate a diff anyway,
     probably with undesirable results.
 
+    Use the --git option to generate diffs in the git extended diff
+    format. Read the gitdiffs help topic for more information.
+
     With the --switch-parent option, the diff will be against the second
     parent. It can be useful to review a merge.
     """