[PATCH v2 2/2] emacs: tag: allow non-automatically-reversible tag operations

[Mark Walters]

This lets the user specify some tag changes as #tag or =tag which mean
the same as +tag and -tag except the reverse changes are not applied
when reversing the operation.
---
 emacs/notmuch-tag.el | 33 +++++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 10 deletions(-)

diff --git a/emacs/notmuch-tag.el b/emacs/notmuch-tag.el
index 2fdccb6..b18dbf0 100644
--- a/emacs/notmuch-tag.el
+++ b/emacs/notmuch-tag.el
@@ -50,7 +50,7 @@
     (,(kbd "u") notmuch-show-mark-read-tags "Mark read")
     (,(kbd "f") ("+flagged") "Flag")
     (,(kbd "s") ("+spam" "-inbox") "Mark as spam")
-    (,(kbd "d") ("+deleted" "-inbox") "Delete"))
+    (,(kbd "d") ("+deleted" "=inbox") "Delete"))
   "A list of keys and corresponding tagging operations
 
 For each key (or key sequence) you can specify a sequence of
@@ -463,14 +463,27 @@ notmuch-after-tag-hook will be run."
 
 Add a \"+\" prefix to any tag in TAGS list that doesn't already
 begin with a \"+\" or a \"-\". If REVERSE is non-nil, replace all
-\"+\" prefixes with \"-\" and vice versa in the result."
-  (mapcar (lambda (str)
-	    (let ((s (if (string-match "^[+-]" str) str (concat "+" str))))
-	      (if reverse
-		  (concat (if (= (string-to-char s) ?-) "+" "-")
-			  (substring s 1))
-		s)))
-	  tags))
+\"+\" prefixes with \"-\" and vice versa in the result.
+
+Tags may also start with \"#\" or \"=\" which mean the same as +
+or - (respectively) when the forward operation is done, but are
+dropped when REVERSE is non-nil."
+  (remove-if 'null
+	     (mapcar (lambda (str)
+		       (let* ((s (if (string-match "^[+#=-]" str)
+				     str
+				   (concat "+" str)))
+			      (change (string-to-char s))
+			      (tag (substring s 1)))
+			 ;; we have a no-op if reverse and # or =
+			 (unless (and reverse (or (= change ?#) (= change ?=)))
+			   (let ((real-change (if reverse
+						  (if (= change ?-) "+" "-")
+						(case change
+						  ((?+ ?#) "+")
+						  ((?- ?=) "-")))))
+			     (concat real-change tag)))))
+		     tags)))
 
 (defun notmuch-tag-jump (reverse)
   (interactive "P")
@@ -486,7 +499,7 @@ begin with a \"+\" or a \"-\". If REVERSE is non-nil, replace all
 				   (second binding)))
 	     (tag-change (if reverse
 			     (notmuch-tag-change-list forward-tag-change 't)
-			   forward-tag-change))
+			   (notmuch-tag-change-list forward-tag-change)))
 	     (name (or (and (not (string= (third binding) ""))
 			    (third binding))
 		       (and (symbolp (second binding))
-- 
2.1.4