Here is a new version of the patch incorporating all the review comments. 
I have rebased it on master so, in particular, it fits into the recently
committed customization framework.

To deal with one corner case I decided to go with Austin's suggestion of 
using lexical-let as it is probably more robust to changes in mm-decode.
I would like to thank him for  all his other help improving my original 
patch.

It passes the test-suite and all cases I can think of work correctly.

Best wishes

Mark



Mark Walters (1):
  Make buttons for attachments allow viewing as well as saving

 emacs/notmuch-show.el |  116 ++++++++++++++++++++++++++++++++++++++----------
 1 files changed, 92 insertions(+), 24 deletions(-)

-- 
1.7.2.3