emacs: Use interactive specifications for tag changes in search

This is similar to the previous commit, but applies to search.

Search is somewhat more complicated because its tagging operations can
also apply to a region.  Hence, this lifts interactive prompting into
a helper function.  This also takes advantage of the new ability to
provide a prompt to distinguish tagging a single thread from tagging a
region of threads.

emacs/notmuch.el

@@ -561,43 +561,62 @@ will be signaled."
 	(setq output (append output (notmuch-search-get-tags pos)))))
     output))
 
-(defun notmuch-search-tag-region (beg end &optional tag-changes)
+(defun notmuch-search-interactive-region ()
-  "Change tags for threads in the given region."
+  "Return the bounds of the current interactive region.
+
+This returns (BEG END), where BEG and END are the bounds of the
+region if the region is active, or both `point' otherwise."
+  (if (region-active-p)
+      (list (region-beginning) (region-end))
+    (list (point) (point))))
+
+(defun notmuch-search-interactive-tag-changes (&optional initial-input)
+  "Prompt for tag changes for the current thread or region.
+
+Returns (TAG-CHANGES REGION-BEGIN REGION-END)."
+  (let* ((region (notmuch-search-interactive-region))
+	 (beg (first region)) (end (second region))
+	 (prompt (if (= beg end) "Tag thread" "Tag region")))
+    (cons (notmuch-read-tag-changes
+	   (notmuch-search-get-tags-region beg end) prompt initial-input)
+	  region)))
+
+(defun notmuch-search-tag (tag-changes &optional beg end)
+  "Change tags for the currently selected thread or region.
+
+See `notmuch-tag' for information on the format of TAG-CHANGES.
+When called interactively, this uses the region if the region is
+active.  When called directly, BEG and END provide the region.
+If these are nil or not provided, this applies to the thread at
+point."
+  (interactive (notmuch-search-interactive-tag-changes))
+  (unless (and beg end) (setq beg (point) end (point)))
   (let ((search-string (notmuch-search-find-thread-id-region-search beg end)))
-    (setq tag-changes (notmuch-tag search-string tag-changes))
+    (notmuch-tag search-string tag-changes)
     (notmuch-search-foreach-result beg end
       (lambda (pos)
 	(notmuch-search-set-tags
 	 (notmuch-update-tags (notmuch-search-get-tags pos) tag-changes)
 	 pos)))))
 
-(defun notmuch-search-tag (&optional tag-changes)
+(defun notmuch-search-add-tag (tag-changes &optional beg end)
-  "Change tags for the currently selected thread or region.
+  "Change tags for the current thread or region (defaulting to add).
-
-See `notmuch-tag' for information on the format of TAG-CHANGES."
-  (interactive)
-  (let* ((beg (if (region-active-p) (region-beginning) (point)))
-	 (end (if (region-active-p) (region-end) (point))))
-    (notmuch-search-tag-region beg end tag-changes)))
-
-(defun notmuch-search-add-tag ()
-  "Change tags for the current thread (defaulting to add).
 
 Same as `notmuch-search-tag' but sets initial input to '+'."
-  (interactive)
+  (interactive (notmuch-search-interactive-tag-changes "+"))
-  (notmuch-search-tag "+"))
+  (notmuch-search-tag tag-changes beg end))
 
-(defun notmuch-search-remove-tag ()
+(defun notmuch-search-remove-tag (tag-changes &optional beg end)
-  "Change tags for the current thread (defaulting to remove).
+  "Change tags for the current thread or region (defaulting to remove).
 
 Same as `notmuch-search-tag' but sets initial input to '-'."
-  (interactive)
+  (interactive (notmuch-search-interactive-tag-changes "-"))
-  (notmuch-search-tag "-"))
+  (notmuch-search-tag tag-changes beg end))
 
 (put 'notmuch-search-archive-thread 'notmuch-prefix-doc
      "Un-archive the currently selected thread.")
-(defun notmuch-search-archive-thread (&optional unarchive)
+(defun notmuch-search-archive-thread (&optional unarchive beg end)
-  "Archive the currently selected thread.
+  "Archive the currently selected thread or region.
 
 Archive each message in the currently selected thread by applying
 the tag changes in `notmuch-archive-tags' to each (remove the
@@ -606,10 +625,10 @@ messages will be \"unarchived\" (i.e. the tag changes in
 `notmuch-archive-tags' will be reversed).
 
 This function advances the next thread when finished."
-  (interactive "P")
+  (interactive (cons current-prefix-arg (notmuch-search-interactive-region)))
   (when notmuch-archive-tags
     (notmuch-search-tag
-     (notmuch-tag-change-list notmuch-archive-tags unarchive)))
+     (notmuch-tag-change-list notmuch-archive-tags unarchive) beg end))
   (notmuch-search-next-thread))
 
 (defun notmuch-search-update-result (result &optional pos)
@@ -833,11 +852,13 @@ non-authors is found, assume that all of the authors match."
 	(notmuch-sexp-parse-partial-list 'notmuch-search-show-result
 					 results-buf)))))
 
-(defun notmuch-search-tag-all (&optional tag-changes)
+(defun notmuch-search-tag-all (tag-changes)
   "Add/remove tags from all messages in current search buffer.
 
 See `notmuch-tag' for information on the format of TAG-CHANGES."
-  (interactive)
+  (interactive
+   (list (notmuch-read-tag-changes
+	  (notmuch-search-get-tags-region (point-min) (point-max)) "Tag all")))
   (notmuch-tag notmuch-search-query-string tag-changes))
 
 (defun notmuch-search-buffer-title (query)