[PATCH] doc: add minimal note about shared options.

[David Bremner]

The example is necessarily a forward reference, but hopefully better
than nothing.
---
 doc/man1/notmuch.rst | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/doc/man1/notmuch.rst b/doc/man1/notmuch.rst
index b33738e..b91db7d 100644
--- a/doc/man1/notmuch.rst
+++ b/doc/man1/notmuch.rst
@@ -49,6 +49,10 @@ Supported global options for ``notmuch`` include
         Specify the configuration file to use. This overrides any
         configuration file specified by ${NOTMUCH\_CONFIG}.
 
+All global options except ``--config`` can also be specified after the
+command. For example, ``notmuch tag --help`` is equivalent to
+``notmuch help tag``.
+
 COMMANDS
 ========
 
-- 
2.1.4