[PATCH 6/7] emacs: Special handling for version mismatch errors

[Austin Clements]

Since Emacs has more semantic information, we suppress the generic
format version error from the CLI and give a more informative error.
---
 emacs/notmuch-lib.el |   11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/emacs/notmuch-lib.el b/emacs/notmuch-lib.el
index 8f84087..9ec30ea 100644
--- a/emacs/notmuch-lib.el
+++ b/emacs/notmuch-lib.el
@@ -360,9 +360,18 @@ giving the output of command.  ERR-FILE, if provided, is the name
 of a file containing the error output of command.  OUTPUT and the
 contents of ERR-FILE will be included in the error message."
 
-  ;; This is implemented as a cond to make it easy to expand.
   (cond
    ((eq exit-status 0) t)
+   ((eq exit-status 20)
+    (notmuch-pop-up-error "Error: Version mismatch.
+Emacs requested an older output format than supported by the notmuch CLI.
+You may need to restart Emacs or upgrade your notmuch Emacs package.")
+    (error "notmuch CLI version mismatch"))
+   ((eq exit-status 21)
+    (notmuch-pop-up-error "Error: Version mismatch.
+Emacs requested a newer output format than supported by the notmuch CLI.
+You may need to restart Emacs or upgrade your notmuch package.")
+    (error "notmuch CLI version mismatch"))
    (t
     (notmuch-pop-up-error
      (concat
-- 
1.7.10.4