org-capture: Inserting an entry doesn't break structure

* lisp/org-capture.el (org-capture-place-entry): Carefully narrow
  buffer to not alter following headline.  Also include leading empty
  lines in region to remove when cancelling capture.
* testing/lisp/test-org-capture.el (test-org-caputre/entry): New test.
(test-org-capture/abort): Rename test.

Reported-by: Martin Yrjölä <martin.yrjola@gmail.com>
<http://lists.gnu.org/r/emacs-orgmode/2018-10/msg00256.html>

lisp/org-capture.el

@@ -1128,20 +1128,20 @@ may have been stored before."
       (unless (org-at-heading-p) (outline-next-heading)))
      ;; Otherwise, insert as a top-level entry at the end of the file.
      (t (goto-char (point-max))))
-    (unless (bolp) (insert "\n"))
-    (org-capture-empty-lines-before)
     (let ((beg (point))
 	  (template (org-capture-get :template)))
+      (unless (bolp) (insert "\n"))
+      (org-capture-empty-lines-before)
       (org-capture-verify-tree template)
       (org-paste-subtree level template 'for-yank)
       (org-capture-empty-lines-after)
       (org-capture-position-for-last-stored beg)
       (unless (org-at-heading-p) (outline-next-heading))
-      (let ((end (point)))
-	(org-capture-mark-kill-region beg end)
+      (org-capture-mark-kill-region beg (point))
+      (let ((end (if (org-at-heading-p) (line-end-position 0) (point))))
 	(org-capture-narrow beg end)
-	(when (or (re-search-backward "%\\?" beg t)
-		  (re-search-forward "%\\?" end t))
+	(when (or (search-backward "%?" beg t)
+		  (search-forward "%?" end t))
 	  (replace-match ""))))))
 
 (defun org-capture-place-item ()

testing/lisp/test-org-capture.el

@@ -145,7 +145,7 @@
 	     (org-capture-refile)
 	     (list file1 file2 (buffer-file-name)))))))))
 
-(ert-deftest test-org-capture/insert-at-end-abort ()
+(ert-deftest test-org-capture/abort ()
   "Test that capture can be aborted after inserting at end of capture buffer."
   (should
    (equal
@@ -160,6 +160,22 @@
 	(org-capture-kill))
       (buffer-string)))))
 
+(ert-deftest test-org-caputre/entry ()
+  "Test `entry' type in capture template."
+  ;; Do not break next headline.
+  (should
+   (equal
+    "* A\n** H1 Capture text\n* B\n"
+    (org-test-with-temp-text-in-file "* A\n* B\n"
+      (let* ((file (buffer-file-name))
+	     (org-capture-templates
+	      `(("t" "Todo" entry (file+headline ,file "A") "** H1 %?"))))
+	(org-capture nil "t")
+	(goto-char (point-max))
+	(insert "Capture text")
+	(org-capture-finalize))
+      (buffer-string)))))
+
 (ert-deftest test-org-capture/table-line ()
   "Test `table-line' type in capture template."
   ;; When a only file is specified, use the first table available.