org-fixup-indentation: Fix regression in logbook adjustment

* lisp/org.el (org-fixup-indentation): Don't call indent-line-to with
a negative value.
* testing/lisp/test-org.el (test-org/promote):
(test-org/demote): Add tests.

The handling added in 11ef7454a (org.el (org-fixup-indentation): Fix
logbook drawers indentation, 2020-09-07) calls indent-line-to with a
value equal to the sum of current indentation and the DIFF argument,
but this can lead to a type error because DIFF may be negative.

Note that, aside from the headline-data test cases, the added tests on
top of the parent of e3b79ad2b (Allow a new value for
`org-adapt-indentation', 2020-02-09), which added the initial logbook
special case to org-fixup-indentation.

Reported-by: Duianto <otnaiud@gmail.com>
Ref: https://orgmode.org/list/CAE-tX7i5ew3ED3YX6jjx57qNuRtV0AumWKuE0W83YUUReKE5-g@mail.gmail.com
Reported-by: stardiviner <numbchild@gmail.com>
Ref: https://orgmode.org/list/CAL1eYuKObYzY2MHSQ+W08mW3TZ+83H45teOq_rHq9qz7-FEgKw@mail.gmail.com

lisp/org.el

@@ -7382,10 +7382,11 @@ Assume point is at a heading or an inlinetask beginning."
      (org-indent-region (match-beginning 0) (match-end 0)))
    (when (looking-at org-logbook-drawer-re)
      (let ((end-marker  (move-marker (make-marker) (match-end 0)))
-	   (ci (current-indentation)))
-       (while (and (not (> (point) end-marker)) (>= ci diff))
-	 (indent-line-to (+ ci diff))
-	 (forward-line))))
+	   (col (+ (current-indentation) diff)))
+       (when (wholenump col)
+	 (while (< (point) end-marker)
+	   (indent-line-to col)
+	   (forward-line)))))
    (catch 'no-shift
      (when (or (zerop diff) (not (eq org-adapt-indentation t)))
        (throw 'no-shift nil))

testing/lisp/test-org.el

@@ -4710,6 +4710,32 @@ Text.
 	    (org-demote)
 	    (forward-line 2)
 	    (org-get-indentation))))))
+  ;; When `org-adapt-indentation' is non-nil, log drawers are
+  ;; adjusted.
+  (should
+   (equal
+    "** H\n   :LOGBOOK:\n   - a\n   :END:\n   b"
+    (org-test-with-temp-text "* H\n  :LOGBOOK:\n  - a\n  :END:\n  b"
+      (let ((org-odd-levels-only nil)
+	    (org-adapt-indentation t))
+	(org-demote))
+      (buffer-string))))
+  (should
+   (equal
+    "** H\n   :LOGBOOK:\n   - a\n   :END:\n  b"
+    (org-test-with-temp-text "* H\n  :LOGBOOK:\n  - a\n  :END:\n  b"
+      (let ((org-odd-levels-only nil)
+	    (org-adapt-indentation 'headline-data))
+	(org-demote))
+      (buffer-string))))
+  (should
+   (equal
+    "** H\n :LOGBOOK:\n - a\n :END:"
+    (org-test-with-temp-text "* H\n:LOGBOOK:\n- a\n:END:"
+      (let ((org-odd-levels-only nil)
+	    (org-adapt-indentation t))
+	(org-demote))
+      (buffer-string))))
   ;; Ignore contents of source blocks or example blocks when
   ;; indentation should be preserved (through
   ;; `org-src-preserve-indentation' or "-i" flag).
@@ -4878,6 +4904,41 @@ Text.
 	  (org-promote))
 	(forward-line)
 	(org-get-indentation))))
+  ;; When `org-adapt-indentation' is non-nil, log drawers are
+  ;; adjusted.
+  (should
+   (equal
+    "* H\n  :LOGBOOK:\n  - a\n  :END:\n  b"
+    (org-test-with-temp-text "** H\n   :LOGBOOK:\n   - a\n   :END:\n   b"
+      (let ((org-odd-levels-only nil)
+	    (org-adapt-indentation t))
+	(org-promote))
+      (buffer-string))))
+  (should
+   (equal
+    "* H\n  :LOGBOOK:\n  - a\n  :END:\n   b"
+    (org-test-with-temp-text "** H\n   :LOGBOOK:\n   - a\n   :END:\n   b"
+      (let ((org-odd-levels-only nil)
+	    (org-adapt-indentation 'headline-data))
+	(org-promote))
+      (buffer-string))))
+  (should
+   (equal
+    "* H\n:LOGBOOK:\n- a\n:END:"
+    (org-test-with-temp-text "** H\n:LOGBOOK:\n- a\n:END:"
+      (let ((org-odd-levels-only nil)
+	    (org-adapt-indentation t))
+	(org-promote))
+      (buffer-string))))
+  (should
+   (equal
+    "# H\n:LOGBOOK:\n- a\n:END:"
+    (org-test-with-temp-text "* H\n:LOGBOOK:\n- a\n:END:"
+      (let ((org-odd-levels-only nil)
+	    (org-allow-promoting-top-level-subtree t)
+	    (org-adapt-indentation t))
+	(org-promote))
+      (buffer-string))))
   ;; Ignore contents of source blocks or example blocks when
   ;; indentation should be preserved (through
   ;; `org-src-preserve-indentation' or "-i" flag).