Since the part commands are no longer tied to a button, but can be
applied with point anywhere within a part, bind the part commands
keymap to "." everywhere in the show buffer.  This lets you save or
view parts without having to navigate to the part button, and is
particularly useful for parts that have no button.  These key bindings
are still available without the prefix when point is over a part
button.
---
 emacs/notmuch-show.el |   27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/emacs/notmuch-show.el b/emacs/notmuch-show.el
index b33d92d..380b144 100644
--- a/emacs/notmuch-show.el
+++ b/emacs/notmuch-show.el
@@ -471,17 +471,6 @@ message at DEPTH in the current thread."
   'face 'message-mml
   :supertype 'notmuch-button-type)
 
-(defvar notmuch-show-part-button-map
-  (let ((map (make-sparse-keymap)))
-    (set-keymap-parent map button-map)
-    (define-key map "s" 'notmuch-show-save-part)
-    (define-key map "v" 'notmuch-show-view-part)
-    (define-key map "o" 'notmuch-show-interactively-view-part)
-    (define-key map "|" 'notmuch-show-pipe-part)
-    map)
-  "Submap for button commands")
-(fset 'notmuch-show-part-button-map notmuch-show-part-button-map)
-
 (defun notmuch-show-insert-part-header (nth content-type declared-type &optional name comment)
   (let ((button)
 	(base-label (concat (when name (concat name ": "))
@@ -1195,6 +1184,21 @@ reset based on the original query."
   "Submap for stash commands")
 (fset 'notmuch-show-stash-map notmuch-show-stash-map)
 
+(defvar notmuch-show-part-map
+  (let ((map (make-sparse-keymap)))
+    (define-key map "s" 'notmuch-show-save-part)
+    (define-key map "v" 'notmuch-show-view-part)
+    (define-key map "o" 'notmuch-show-interactively-view-part)
+    (define-key map "|" 'notmuch-show-pipe-part)
+    map)
+  "Submap for part commands")
+(fset 'notmuch-show-part-map notmuch-show-part-map)
+
+(defvar notmuch-show-part-button-map
+  (make-composed-keymap notmuch-show-part-map button-map)
+  "Keymap for part button commands")
+(fset 'notmuch-show-part-button-map notmuch-show-part-button-map)
+
 (defvar notmuch-show-mode-map
       (let ((map (make-sparse-keymap)))
 	(define-key map "?" 'notmuch-help)
@@ -1237,6 +1241,7 @@ reset based on the original query."
 	(define-key map "$" 'notmuch-show-toggle-process-crypto)
 	(define-key map "<" 'notmuch-show-toggle-thread-indentation)
 	(define-key map "t" 'toggle-truncate-lines)
+	(define-key map "." 'notmuch-show-part-map)
 	map)
       "Keymap for \"notmuch show\" buffers.")
 (fset 'notmuch-show-mode-map notmuch-show-mode-map)
-- 
1.7.10.4