Backport commit c75f505de from Emacs

* lisp/org-agenda.el (org-agenda-to-appt):
* lisp/org-clock.el (org-clock-resolve-clock)
(org-clock-resolve, org-resolve-clocks-if-idle):
* lisp/org-colview.el (org-columns-edit-value, org-columns)
(org-agenda-columns):
* lisp/org-element.el (org-element--cache-interrupt-p)
(org-element--cache-sync):
* lisp/org-habit.el (org-habit-get-faces)
(org-habit-insert-consistency-graphs):
* lisp/org-indent.el (org-indent-add-properties):
* lisp/org-timer.el ((org-timer-show-remaining-time):
* lisp/org.el (org-babel-load-file, org-current-time)
(org-today, org-auto-repeat-maybe)
(org-small-year-to-year, org-goto-calendar):
* lisp/ox.el (org-export-insert-default-template):
Use nil instead of (current-time) where either will do, as nil is
a bit more efficient and should have less timing error.

Prefer nil to (current-time) when either works
c75f505dea6a560b825384cf3d277690f86840bf
Paul Eggert
Fri Oct 20 19:42:23 2017 -0700

Note(km): The changes that will reverted in the next commit have been
dropped from the ChangeLog entries above.

lisp/org-agenda.el

@@ -10201,7 +10201,7 @@ to override `appt-message-warning-time'."
          ;; time and without date as argument, so it may pass wrong
          ;; information otherwise
          (today (org-date-to-gregorian
-                 (time-to-days (current-time))))
+                 (time-to-days nil)))
          (org-agenda-restrict nil)
          (files (org-agenda-files 'unrestricted)) entries file
          (org-agenda-buffer nil))

lisp/org-clock.el

@@ -943,7 +943,7 @@ CLOCK is a cons cell of the form (MARKER START-TIME)."
 	 (org-clock-clock-out clock fail-quietly))
 	((org-is-active-clock clock) nil)
 	(t (org-clock-clock-in clock t))))
-      ((pred (time-less-p (current-time)))
+      ((pred (time-less-p nil))
        (error "RESOLVE-TO must refer to a time in the past"))
       (_
        (when restart (error "RESTART is not valid here"))
@@ -1043,7 +1043,7 @@ to be CLOCKED OUT."))))
 		(and (not (memq char-pressed '(?i ?q))) char-pressed)))))
 	 (default
 	   (floor (/ (float-time
-		      (time-subtract (current-time) last-valid)) 60)))
+		      (time-subtract nil last-valid)) 60)))
 	 (keep
 	  (and (memq ch '(?k ?K))
 	       (read-number "Keep how many minutes? " default)))
@@ -1080,8 +1080,7 @@ to be CLOCKED OUT."))))
 	      (keep
 	       (time-add last-valid (seconds-to-time (* 60 keep))))
 	      (gotback
-	       (time-subtract (current-time)
-			      (seconds-to-time (* 60 gotback))))
+	       (time-subtract nil (seconds-to-time (* 60 gotback))))
 	      (t
 	       (error "Unexpected, please report this as a bug")))
        (and gotback last-valid)
@@ -1163,7 +1162,7 @@ so long."
 	     org-clock-marker (marker-buffer org-clock-marker))
     (let* ((org-clock-user-idle-seconds (org-user-idle-seconds))
 	   (org-clock-user-idle-start
-	    (time-subtract (current-time)
+	    (time-subtract nil
 			   (seconds-to-time org-clock-user-idle-seconds)))
 	   (org-clock-resolving-clocks-due-to-idleness t))
       (if (> org-clock-user-idle-seconds (* 60 org-clock-idle-time))
@@ -1173,8 +1172,7 @@ so long."
 	   (lambda (_)
 	     (format "Clocked in & idle for %.1f mins"
 		     (/ (float-time
-			 (time-subtract (current-time)
-					org-clock-user-idle-start))
+			 (time-subtract nil org-clock-user-idle-start))
 			60.0)))
 	   org-clock-user-idle-start)))))
 

lisp/org-colview.el

@@ -579,7 +579,7 @@ Where possible, use the standard interface for changing this line."
 	 (eol (line-end-position))
 	 (pom (or (get-text-property bol 'org-hd-marker) (point)))
 	 (key (or key (get-char-property (point) 'org-columns-key)))
-	 (org-columns--time (float-time (current-time)))
+	 (org-columns--time (float-time))
 	 (action
 	  (pcase key
 	    ("CLOCKSUM"
@@ -830,7 +830,7 @@ When COLUMNS-FMT-STRING is non-nil, use it as the column format."
     (org-columns-goto-top-level)
     ;; Initialize `org-columns-current-fmt' and
     ;; `org-columns-current-fmt-compiled'.
-    (let ((org-columns--time (float-time (current-time))))
+    (let ((org-columns--time (float-time)))
       (org-columns-get-format columns-fmt-string)
       (unless org-columns-inhibit-recalculation (org-columns-compute-all))
       (save-restriction
@@ -1224,7 +1224,7 @@ column specification."
   "Compute all columns that have operators defined."
   (with-silent-modifications
     (remove-text-properties (point-min) (point-max) '(org-summaries t)))
-  (let ((org-columns--time (float-time (current-time)))
+  (let ((org-columns--time (float-time))
 	seen)
     (dolist (spec org-columns-current-fmt-compiled)
       (let ((property (car spec)))
@@ -1560,7 +1560,7 @@ PARAMS is a property list of parameters:
   (if (markerp org-columns-begin-marker)
       (move-marker org-columns-begin-marker (point))
     (setq org-columns-begin-marker (point-marker)))
-  (let* ((org-columns--time (float-time (current-time)))
+  (let* ((org-columns--time (float-time))
 	 (fmt
 	  (cond
 	   ((bound-and-true-p org-agenda-overriding-columns-format))

lisp/org-element.el

@@ -5114,7 +5114,7 @@ Assume ELEMENT belongs to cache and that a cache is active."
 TIME-LIMIT is a time value or nil."
   (and time-limit
        (or (input-pending-p)
-	   (time-less-p time-limit (current-time)))))
+	   (time-less-p time-limit nil))))
 
 (defsubst org-element--cache-shift-positions (element offset &optional props)
   "Shift ELEMENT properties relative to buffer positions by OFFSET.
@@ -5168,7 +5168,7 @@ updated before current modification are actually submitted."
 	     (and next (aref next 0))
 	     threshold
 	     (and (not threshold)
-		  (time-add (current-time)
+		  (time-add nil
 			    org-element-cache-sync-duration))
 	     future-change)
 	    ;; Request processed.  Merge current and next offsets and

lisp/org-habit.el

@@ -288,7 +288,7 @@ Habits are assigned colors on the following basis:
 	 (deadline (if scheduled-days
 		       (+ scheduled-days (- d-repeat s-repeat))
 		     (org-habit-deadline habit)))
-	 (m-days (or now-days (time-to-days (current-time)))))
+	 (m-days (or now-days (time-to-days nil))))
     (cond
      ((< m-days scheduled)
       '(org-habit-clear-face . org-habit-clear-future-face))
@@ -406,7 +406,7 @@ current time."
   "Insert consistency graph for any habitual tasks."
   (let ((inhibit-read-only t)
 	(buffer-invisibility-spec '(org-link))
-	(moment (time-subtract (current-time)
+	(moment (time-subtract nil
 			       (list 0 (* 3600 org-extend-today-until) 0))))
     (save-excursion
       (goto-char (if line (point-at-bol) (point-min)))

lisp/org-indent.el

@@ -326,7 +326,7 @@ stopped."
      (let* ((case-fold-search t)
 	    (limited-re (org-get-limited-outline-regexp))
 	    (level (or (org-current-level) 0))
-	    (time-limit (and delay (time-add (current-time) delay))))
+	    (time-limit (and delay (time-add nil delay))))
        ;; For each line, set `line-prefix' and `wrap-prefix'
        ;; properties depending on the type of line (headline, inline
        ;; task, item or other).
@@ -339,7 +339,7 @@ stopped."
 	    ;; In asynchronous mode, take a break of
 	    ;; `org-indent-agent-resume-delay' every DELAY to avoid
 	    ;; blocking any other idle timer or process output.
-	    ((and delay (time-less-p time-limit (current-time)))
+	    ((and delay (time-less-p time-limit nil))
 	     (setq org-indent-agent-resume-timer
 		   (run-with-idle-timer
 		    (time-add (current-idle-time) org-indent-agent-resume-delay)

lisp/org-timer.el

@@ -144,7 +144,7 @@ the region 0:00:00."
 	       ;; Pass `current-time' result to `float-time' (instead
 	       ;; of calling without arguments) so that only
 	       ;; `current-time' has to be overridden in tests.
-	       (- (float-time (current-time)) delta))))
+	       (- (float-time) delta))))
       (setq org-timer-pause-time nil)
       (org-timer-set-mode-line 'on)
       (message "Timer start time set to %s, current value is %s"
@@ -169,12 +169,12 @@ With prefix arg STOP, stop it entirely."
 		  (org-timer--run-countdown-timer
 		   new-secs org-timer-countdown-timer-title))
 	    (setq org-timer-start-time
-		  (time-add (current-time) (seconds-to-time new-secs))))
+		  (time-add nil (seconds-to-time new-secs))))
 	(setq org-timer-start-time
 	      ;; Pass `current-time' result to `float-time' (instead
 	      ;; of calling without arguments) so that only
 	      ;; `current-time' has to be overridden in tests.
-	      (seconds-to-time (- (float-time (current-time))
+	      (seconds-to-time (- (float-time)
 				  (- pause-secs start-secs)))))
       (setq org-timer-pause-time nil)
       (org-timer-set-mode-line 'on)
@@ -240,8 +240,8 @@ it in the buffer."
   ;; overridden in tests.
   (if org-timer-countdown-timer
       (- (float-time org-timer-start-time)
-	 (float-time (or org-timer-pause-time (current-time))))
-    (- (float-time (or org-timer-pause-time (current-time)))
+	 (float-time org-timer-pause-time))
+    (- (float-time org-timer-pause-time)
        (float-time org-timer-start-time))))
 
 ;;;###autoload
@@ -402,7 +402,7 @@ VALUE can be `on', `off', or `paused'."
       (message "No timer set")
     (let* ((rtime (decode-time
 		   (time-subtract (timer--time org-timer-countdown-timer)
-				  (current-time))))
+				  nil)))
 	   (rsecs (nth 0 rtime))
 	   (rmins (nth 1 rtime)))
       (message "%d minute(s) %d seconds left before next time out"
@@ -466,7 +466,7 @@ using three `C-u' prefix arguments."
 		 secs org-timer-countdown-timer-title))
 	  (run-hooks 'org-timer-set-hook)
 	  (setq org-timer-start-time
-		(time-add (current-time) (seconds-to-time secs)))
+		(time-add nil (seconds-to-time secs)))
 	  (setq org-timer-pause-time nil)
 	  (org-timer-set-mode-line 'on))))))
 

lisp/org.el

@@ -252,7 +252,7 @@ file to byte-code before it is loaded."
   (interactive "fFile to load: \nP")
   (let* ((age (lambda (file)
 		(float-time
-		 (time-subtract (current-time)
+		 (time-subtract nil
 				(nth 5 (or (file-attributes (file-truename file))
 					   (file-attributes file)))))))
 	 (base-name (file-name-sans-extension file))
@@ -5637,15 +5637,14 @@ the rounding returns a past time."
 	    (apply 'encode-time
 		   (append (list 0 (* r (floor (+ .5 (/ (float (nth 1 time)) r)))))
 			   (nthcdr 2 time))))
-      (if (and past (< (float-time (time-subtract (current-time) res)) 0))
+      (if (and past (< (float-time (time-subtract nil res)) 0))
 	  (seconds-to-time (- (float-time res) (* r 60)))
 	res))))
 
 (defun org-today ()
   "Return today date, considering `org-extend-today-until'."
   (time-to-days
-   (time-subtract (current-time)
-		  (list 0 (* 3600 org-extend-today-until) 0))))
+   (time-subtract nil (list 0 (* 3600 org-extend-today-until) 0))))
 
 ;;;; Font-Lock stuff, including the activators
 
@@ -12792,8 +12791,7 @@ This function is run automatically after each state change to a DONE state."
 		    (while (re-search-forward org-clock-line-re end t)
 		      (when (org-at-clock-log-p) (throw :clock t))))))
 	(org-entry-put nil "LAST_REPEAT" (format-time-string
-					  (org-time-stamp-format t t)
-					  (current-time))))
+					  (org-time-stamp-format t t))))
       (when org-log-repeat
 	(if (or (memq 'org-add-log-note (default-value 'post-command-hook))
 		(memq 'org-add-log-note post-command-hook))
@@ -12848,7 +12846,7 @@ This function is run automatically after each state change to a DONE state."
 		      (let ((nshiftmax 10)
 			    (nshift 0))
 			(while (or (= nshift 0)
-				   (not (time-less-p (current-time) time)))
+				   (not (time-less-p nil time)))
 			  (when (= nshiftmax (cl-incf nshift))
 			    (or (y-or-n-p
 				 (format "%d repeater intervals were not \
@@ -16401,7 +16399,7 @@ user."
   ;; overridden in tests.
   (let ((org-def def)
 	(org-defdecode defdecode)
-	(nowdecode (decode-time (current-time)))
+	(nowdecode (decode-time))
 	delta deltan deltaw deltadef year month day
 	hour minute second wday pm h2 m2 tl wday1
 	iso-year iso-weekday iso-week iso-date futurep kill-year)
@@ -16567,7 +16565,7 @@ user."
 					;      (when (and org-read-date-prefer-future
 					;		 (not iso-year)
 					;		 (< (calendar-absolute-from-gregorian iso-date)
-					;		    (time-to-days (current-time))))
+					;		    (time-to-days nil)))
 					;	(setq year (1+ year)
 					;	      iso-date (calendar-gregorian-from-absolute
 					;			(calendar-iso-to-absolute
@@ -16581,7 +16579,7 @@ user."
 	;; Pass `current-time' result to `decode-time' (instead of
 	;; calling without arguments) so that only `current-time' has
 	;; to be overridden in tests.
-	(let ((now (decode-time (current-time))))
+	(let ((now (decode-time)))
 	  (setq day (nth 3 now) month (nth 4 now) year (nth 5 now))))
       (cond ((member deltaw '("d" "")) (setq day (+ day deltan)))
 	    ((equal deltaw "w") (setq day (+ day (* 7 deltan))))
@@ -17055,7 +17053,7 @@ signaled."
 YEAR is expanded into one of the 30 next years, if possible, or
 into a past one.  Any year larger than 99 is returned unchanged."
   (if (>= year 100) year
-    (let* ((current (string-to-number (format-time-string "%Y" (current-time))))
+    (let* ((current (string-to-number (format-time-string "%Y")))
 	   (century (/ current 100))
 	   (offset (- year (% current 100))))
       (cond ((> offset 30) (+ (* (1- century) 100) year))
@@ -17552,7 +17550,7 @@ A prefix ARG can be used to force the current date."
 	diff)
     (when (or (org-at-timestamp-p 'lax)
 	      (org-match-line (concat ".*" org-ts-regexp)))
-      (let ((d1 (time-to-days (current-time)))
+      (let ((d1 (time-to-days nil))
 	    (d2 (time-to-days (org-time-string-to-time (match-string 1)))))
 	(setq diff (- d2 d1))))
     (calendar)

lisp/ox.el

@@ -3230,7 +3230,7 @@ locally for the subtree through node properties."
       (let ((val (cond ((equal (car key) "DATE")
 			(or (cdr key)
 			    (with-temp-buffer
-			      (org-insert-time-stamp (current-time)))))
+			      (org-insert-time-stamp nil))))
 		       ((equal (car key) "TITLE")
 			(or (let ((visited-file
 				   (buffer-file-name (buffer-base-buffer))))