notmuch.el: Clean up documentation of notmuch-search-mode-map commands.

Since notmuch-help now displays a single line of documentation from
each of these commands we ensure that the first line stands alone for
each command.

We also override some builtin commands with new commands that don't
behave any differently, but have our own notmuch-specific
documentation, (such as "select next thread" rather than "move point
to next line").

notmuch.el

@@ -933,10 +933,10 @@ thread from that buffer can be show when done with this one)."
     (define-key map (kbd "<DEL>") 'notmuch-search-scroll-down)
     (define-key map "b" 'notmuch-search-scroll-down)
     (define-key map " " 'notmuch-search-scroll-up)
-    (define-key map "<" 'beginning-of-buffer)
-    (define-key map ">" 'notmuch-search-goto-last-thread)
-    (define-key map "p" 'previous-line)
-    (define-key map "n" 'next-line)
+    (define-key map "<" 'notmuch-search-first-thread)
+    (define-key map ">" 'notmuch-search-last-thread)
+    (define-key map "p" 'notmuch-search-previous-thread)
+    (define-key map "n" 'notmuch-search-next-thread)
     (define-key map "r" 'notmuch-search-reply-to-thread)
     (define-key map "m" 'message-mail)
     (define-key map "s" 'notmuch-search)
@@ -958,16 +958,15 @@ thread from that buffer can be show when done with this one)."
 (defvar notmuch-search-oldest-first t
   "Show the oldest mail first in the search-mode")
 
-
 (defun notmuch-search-scroll-up ()
-  "Scroll up, moving point to last message in thread if at end."
+  "Move forward through search results by one window's worth."
   (interactive)
   (condition-case nil
       (scroll-up nil)
-    ((end-of-buffer) (notmuch-search-goto-last-thread))))
+    ((end-of-buffer) (notmuch-search-last-thread))))
 
 (defun notmuch-search-scroll-down ()
-  "Scroll down, moving point to first message in thread if at beginning."
+  "Move backward through the search results by one window's worth."
   (interactive)
   ; I don't know why scroll-down doesn't signal beginning-of-buffer
   ; the way that scroll-up signals end-of-buffer, but c'est la vie.
@@ -981,12 +980,27 @@ thread from that buffer can be show when done with this one)."
       (goto-char (point-min))
     (scroll-down nil)))
 
-(defun notmuch-search-goto-last-thread ()
-  "Move point to the last thread in the buffer."
+(defun notmuch-search-next-thread ()
+  "Select the next thread in the search results."
+  (interactive)
+  (next-line))
+
+(defun notmuch-search-previous-thread ()
+  "Select the previous thread in the search results."
+  (interactive)
+  (previous-line))
+
+(defun notmuch-search-last-thread ()
+  "Select the last thread in the search results."
   (interactive)
   (goto-char (point-max))
   (forward-line -2))
 
+(defun notmuch-search-first-thread ()
+  "Select the first thread in the search results."
+  (interactive)
+  (goto-char (point-min)))
+
 (defface notmuch-tag-face
   '((((class color)
       (background dark))
@@ -1110,25 +1124,29 @@ and will also appear in a buffer named \"*Notmuch errors*\"."
 	(split-string (buffer-substring beg end))))))
 
 (defun notmuch-search-add-tag (tag)
-  "Add a tag to messages in the current thread matching the
-active query."
+  "Add a tag to the currently selected thread.
+
+The tag is added to messages in the currently selected thread
+which match the current search terms."
   (interactive
    (list (notmuch-select-tag-with-completion "Tag to add: ")))
   (notmuch-call-notmuch-process "tag" (concat "+" tag) (notmuch-search-find-thread-id) " and " notmuch-search-query-string)
   (notmuch-search-set-tags (delete-dups (sort (cons tag (notmuch-search-get-tags)) 'string<))))
 
 (defun notmuch-search-remove-tag (tag)
-  "Remove a tag from messages in the current thread matching the
-active query."
+  "Remove a tag from the currently selected thread.
+
+The tag is removed from messages in the currently selected thread
+which match the current search terms."
   (interactive
    (list (notmuch-select-tag-with-completion "Tag to remove: " (notmuch-search-find-thread-id))))
   (notmuch-call-notmuch-process "tag" (concat "-" tag) (notmuch-search-find-thread-id) " and " notmuch-search-query-string)
   (notmuch-search-set-tags (delete tag (notmuch-search-get-tags))))
 
 (defun notmuch-search-archive-thread ()
-  "Archive the current thread (remove its \"inbox\" tag).
+  "Archive the currently selected thread (remove its \"inbox\" tag).
 
-This function advances point to the next line when finished."
+This function advances the next thread when finished."
   (interactive)
   (notmuch-search-remove-tag "inbox")
   (forward-line))
@@ -1182,12 +1200,12 @@ This function advances point to the next line when finished."
       (delete-process proc))))
 
 (defun notmuch-search-operate-all (action)
-  "Operate on all messages matching the current query.  Any
-number of whitespace separated actions can be given.  Each action
-must have one of the two forms
+  "Add/remove tags from all matching messages.
 
-  +tagname              Add the tag `tagname'
-  -tagname              Remove the tag `tagname'
+Tis command adds or removes tags from all messages matching the
+current search terms. When called interactively, this command
+will prompt for tags to be added or removed. Tags prefixed with
+'+' will be added and tags prefixed with '-' will be removed.
 
 Each character of the tag name may consist of alphanumeric
 characters as well as `_.+-'.