From 852385892a293e2a3479846a3f96e98678ba93d3 Mon Sep 17 00:00:00 2001
From: Yasushi SHOJI <address@hidden>
Date: Mon, 14 Jan 2019 10:19:50 +0900
Subject: [PATCH] org-clone: Allow time shift in backward

Make `org-clone-subtree-with-time-shift` accept a negative value to
shift the timestamp in backward.

Reported-by: Scott Randby <address@hidden>
<http://lists.gnu.org/r/emacs-orgmode/2019-01/msg00151.html>

Signed-off-by: Yasushi SHOJI <address@hidden>
---
 etc/ORG-NEWS             |  5 +++++
 lisp/org.el              |  2 +-
 testing/lisp/test-org.el | 12 ++++++++++++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/etc/ORG-NEWS b/etc/ORG-NEWS
index e06d0c09b..4821cfa85 100644
--- a/etc/ORG-NEWS
+++ b/etc/ORG-NEWS
@@ -104,6 +104,11 @@ A 'native option was added to org-highlight-latex-and-related. It
 matches the same structures than 'latex but it calls
 org-src-font-lock-fontify-block instead, thus bringing about full
 LaTeX font locking.
+*** ~org-clone-subtree-with-time-shift~ learnt to shift backward in time
+=<C-c C-x c>= (~org-clone-subtree-with-time-shift~) now takes a
+negative value as a valid repeater to shift time stamps in backward
+in cloned subtrees.  You can give, for example, ‘-3d’ to shift three
+days in the past.
 
 ** New functions
 *** ~org-dynamic-block-insert-dblock~
diff --git a/lisp/org.el b/lisp/org.el
index 5c11de7b6..e71ba73e6 100644
--- a/lisp/org.el
+++ b/lisp/org.el
@@ -8452,7 +8452,7 @@ with the original repeater."
 		"")))			;No time shift
 	 (doshift
 	  (and (org-string-nw-p shift)
-	       (or (string-match "\\`[ \t]*\\+?\\([0-9]+\\)\\([dwmy]\\)[ \t]*\\'"
+	       (or (string-match "\\`[ \t]*\\([\\+\\-]?[0-9]+\\)\\([dwmy]\\)[ \t]*\\'"
 				 shift)
 		   (user-error "Invalid shift specification %s" shift)))))
     (goto-char end-of-tree)
diff --git a/testing/lisp/test-org.el b/testing/lisp/test-org.el
index 976b7d8d6..db34a03c2 100644
--- a/testing/lisp/test-org.el
+++ b/testing/lisp/test-org.el
@@ -1496,6 +1496,18 @@
 	    (replace-regexp-in-string
 	     "\\( [.A-Za-z]+\\)\\( \\+[0-9][hdmwy]\\)?>" "" (buffer-string)
 	     nil nil 1))))
+  ;; Clone repeating once in backward.
+  (should
+   (equal "\
+* H1\n<2015-06-21>
+* H1\n<2015-06-19>
+* H1\n<2015-06-17 +1w>
+"
+	  (org-test-with-temp-text "* H1\n<2015-06-21 Sun +1w>"
+	    (org-clone-subtree-with-time-shift 1 "-2d")
+	    (replace-regexp-in-string
+	     "\\( [.A-Za-z]+\\)\\( \\+[0-9][hdmwy]\\)?>" "" (buffer-string)
+	     nil nil 1))))
   ;; Clone non-repeating zero times.
   (should
    (equal "\
-- 
2.20.1