lisp/org.el (org-sort-entries): Fix sorting partially selected subtree

* lisp/org.el (org-sort-entries): Make sure that we extend sorted
region to the full subtree if it spans beyond end of region.
* testing/lisp/test-org.el (test-org/sort-entries): Add test.

lisp/org.el

@@ -7702,12 +7702,24 @@ function is being called interactively."
     ;; Find beginning and end of region to sort
     (cond
      ((org-region-active-p)
+      (setq start (region-beginning)
+            end (region-end))
       ;; we will sort the region
-      (setq end (region-end)
+      ;; Limit the region to full headings.
+      (goto-char start)
+      ;; Move to beginning of heading.
+      ;; If we are inside heading, move to next.
+      ;; If we are on heading, move to its begin position.
+      (if (org-at-heading-p)
+          (forward-line 0)
+        (outline-next-heading))
+      (setq start (point))
+      ;; Extend region end beyond the last subtree.
+      (goto-char end)
+      (org-end-of-subtree nil t)
+      (setq end (point)
             what "region")
-      (goto-char (region-beginning))
-      (unless (org-at-heading-p) (outline-next-heading))
-      (setq start (point)))
+      (goto-char start))
      ((or (org-at-heading-p)
           (ignore-errors (progn (org-back-to-heading) t)))
       ;; we will sort the children of the current headline

testing/lisp/test-org.el

@@ -3916,7 +3916,25 @@ SCHEDULED: <2017-05-06 Sat>
 	  (org-test-with-temp-text
 	      "\n* B\n* A\n# Local Variables:\n# foo: t\n# End:"
 	    (org-sort-entries nil ?a)
-	    (buffer-string)))))
+	    (buffer-string))))
+  ;; Sort region
+  (should
+   (equal "
+* [#A] h2
+* [#B] h3
+* [#C] h1
+"
+	  (org-test-with-temp-text
+	      "
+<point>* [#C] h1
+* [#A] h2
+* [#B] h3"
+            (transient-mark-mode 1)
+            (push-mark (point) t t)
+            (search-forward "h3")
+	    (org-sort-entries nil ?p)
+	    (buffer-string))))
+  )
 
 (ert-deftest test-org/string-collate-greaterp ()
   "Test `org-string-collate-greaterp' specifications."