[PATCH] org-compat: Allow imenu items without hierarchy

[Michael Hendricks <michael@ndrix.org>]

* lisp/org-compat.el (org-imenu-flat): New custom variable.
(org-imenu-get-tree): Skip hierarchical item structure if
org-imenu-flat is true.

Many of my Org files have deep hierarchies, but few total headings.
For those files, I find that navigating a flat menu structure is more
effective than navigating many nested menus.

A flat imenu structure also works well with packages, such as idomenu,
which navigate imenu items via search.
---
 lisp/org-compat.el | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/lisp/org-compat.el b/lisp/org-compat.el
index e7ea4153e..cb9419857 100644
--- a/lisp/org-compat.el
+++ b/lisp/org-compat.el
@@ -600,6 +600,12 @@ This also applied for speedbar access."
   :group 'org-imenu-and-speedbar
   :type 'integer)
 
+(defcustom org-imenu-flat nil
+  "Non-nil creates index items at the top level.  The default is
+for the index hierarchy to match the buffer's hierarchy."
+  :group 'org-imenu-and-speedbar
+  :type 'boolean)
+
 ;;;; Imenu
 
 (defvar-local org-imenu-markers nil
@@ -618,6 +624,7 @@ This also applied for speedbar access."
   (setq org-imenu-markers nil)
   (let* ((case-fold-search nil)
 	 (n org-imenu-depth)
+	 (flat org-imenu-flat)
 	 (re (concat "^" (org-get-limited-outline-regexp)))
 	 (subs (make-vector (1+ n) nil))
 	 (last-level 0)
@@ -632,10 +639,12 @@ This also applied for speedbar access."
 	 (setq head (org-link-display-format head0)
 	       m (org-imenu-new-marker))
 	 (org-add-props head nil 'org-imenu-marker m 'org-imenu t)
-	 (if (>= level last-level)
-	     (push (cons head m) (aref subs level))
-	   (push (cons head (aref subs (1+ level))) (aref subs level))
-	   (cl-loop for i from (1+ level) to n do (aset subs i nil)))
+	 (if flat
+	     (push (cons head m) (aref subs 1))
+	   (if (>= level last-level)
+	       (push (cons head m) (aref subs level))
+	     (push (cons head (aref subs (1+ level))) (aref subs level))
+	     (cl-loop for i from (1+ level) to n do (aset subs i nil))))
 	 (setq last-level level))))
     (aref subs 1)))
 
-- 
2.14.2