vimish: add accessers for nested non folded folds

vimish-fold.el

@@ -338,6 +338,16 @@ If OVERLAY does not represent a fold, it's ignored."
    #'vimish-fold--vimish-overlay-p
    (overlays-in beg end)))
 
+(defun vimish-fold--folds-beginning-in (beg end)
+  "Returns all the folds beginning if BEG and END in current buffer."
+  (let ((list (vimish-fold--folds-in beg end)) tmp-ov)
+    (while (list)
+      (setq tmp-ov (car list))
+      (unless (and (>= beg (overlay-start tmp-ov))
+                   (<= end (overlay-start tmp-ov)))
+        (delq tmp-ov list))
+      (setq list (cdr list)))))
+
 ;;;###autoload
 (defun vimish-fold-unfold-all ()
   "Unfold all folds in current buffer."
@@ -442,6 +452,26 @@ This feature needs `avy' package."
            folds-before-point)))
       (message "No more folds before point"))))
 
+(defun vimish-fold-previous-existing-fold ()
+  "Jump to previous vimish region in current buffer.
+
+The difference with vimish-fold-previous-fold is that here, the previous
+folds can be englobing folds (see vimish-fold-allow-nested)"
+  (interactive)
+  (let ((folds-before-point
+         (cl-nset-difference
+          (vimish-fold--folds-in (point-min) (point))
+          (vimish-fold--folds-beginning-in (point) (point-max))
+          )))
+    (if folds-before-point
+        (goto-char
+         (cl-reduce
+          #'max
+          (mapcar
+           #'overlay-start
+           folds-before-point)))
+      (message "No more folds before point"))))
+
 
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