New command goto-line-relative (bug#5042, bug#9917)

* lisp/simple.el (goto-line-read-args): New function with code from goto-line.
(goto-line): New arg RELATIVE.  Also use 'widen-automatically' to
leave all lines accessible in the narrowed buffer.
(goto-line-relative): New command.

* lisp/info.el (Info-mode-map): Remap 'goto-line' to 'goto-line-relative'.

* doc/emacs/basic.texi (Moving Point):
* doc/emacs/display.texi (Optional Mode Line): Mention goto-line-relative.

5 files changed, 73 insertions, 33 deletions

diff --git a/doc/emacs/basic.texi b/doc/emacs/basic.texi
index 444b2469cf1..cde7b475d95 100644
--- a/doc/emacs/basic.texi
+++ b/doc/emacs/basic.texi
@@ -311,13 +311,16 @@ Position 1 is the beginning of the buffer.
 @kindex M-g M-g
 @kindex M-g g
 @findex goto-line
+@findex goto-line-relative
 Read a number @var{n} and move point to the beginning of line number
 @var{n} (@code{goto-line}).  Line 1 is the beginning of the buffer.  If
 point is on or just after a number in the buffer, that is the default
 for @var{n}.  Just type @key{RET} in the minibuffer to use it.  You can
 also specify @var{n} by giving @kbd{M-g M-g} a numeric prefix argument.
 @xref{Select Buffer}, for the behavior of @kbd{M-g M-g} when you give it
-a plain prefix argument.
+a plain prefix argument.  Alternatively, you can use the command
+@code{goto-line-relative} to move point to the line relative to the
+accessible portion of the narrowed buffer.
 
 @item M-g @key{TAB}
 @kindex M-g TAB
diff --git a/doc/emacs/display.texi b/doc/emacs/display.texi
index e7b8745a044..6f1bc802b85 100644
--- a/doc/emacs/display.texi
+++ b/doc/emacs/display.texi
@@ -1452,9 +1452,10 @@ the displayed column number to count from one, you may set
 @cindex narrowing, and line number display
   If you have narrowed the buffer (@pxref{Narrowing}), the displayed
 line number is relative to the accessible portion of the buffer.
-Thus, it isn't suitable as an argument to @code{goto-line}.  (Use
-@code{what-line} command to see the line number relative to the whole
-file.)
+Thus, it isn't suitable as an argument to @code{goto-line}.  (The
+command @code{what-line} shows the line number relative to the whole
+file.)  You can use @code{goto-line-relative} command to move point to
+the line relative to the accessible portion of the narrowed buffer.
 
 @vindex line-number-display-limit
   If the buffer is very large (larger than the value of
diff --git a/etc/NEWS b/etc/NEWS
index a4c823072c9..fe2f5c37821 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -172,6 +172,13 @@ Each buffer will keep a separate history of line numbers used with
 line numbers that were previously jumped to.
 
 +++
+** New command 'goto-line-relative' to use in a narrowed buffer.
+It moves point to the line relative to the accessible portion of the
+narrowed buffer.  'M-g M-g' in Info is rebound to this command.
+When 'widen-automatically' is non-nil, 'goto-line' widens the narrowed
+buffer to be able to move point to the inaccessible portion.
+
++++
 ** When 'suggest-key-bindings' is non-nil, the completion list of 'M-x'
 shows equivalent key bindings for all commands that have them.
 
diff --git a/lisp/info.el b/lisp/info.el
index e4f75b481fe..20633fd0598 100644
--- a/lisp/info.el
+++ b/lisp/info.el
@@ -4053,6 +4053,7 @@ If FORK is non-nil, it is passed to `Info-goto-node'."
     (define-key map "^" 'Info-up)
     (define-key map "," 'Info-index-next)
     (define-key map "\177" 'Info-scroll-down)
+    (define-key map [remap goto-line] 'goto-line-relative)
     (define-key map [mouse-2] 'Info-mouse-follow-nearest-node)
     (define-key map [follow-link] 'mouse-face)
     (define-key map [XF86Back] 'Info-history-back)
diff --git a/lisp/simple.el b/lisp/simple.el
index d7486e51ddc..825fec380cb 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -1231,7 +1231,39 @@ that uses or sets the mark."
   "History of values entered with `goto-line'.")
 (make-variable-buffer-local 'goto-line-history)
 
-(defun goto-line (line &optional buffer)
+(defun goto-line-read-args (&optional relative)
+  "Read arguments for `goto-line' related commands."
+  (if (and current-prefix-arg (not (consp current-prefix-arg)))
+      (list (prefix-numeric-value current-prefix-arg))
+    ;; Look for a default, a number in the buffer at point.
+    (let* ((default
+             (save-excursion
+               (skip-chars-backward "0-9")
+               (if (looking-at "[0-9]")
+                   (string-to-number
+                    (buffer-substring-no-properties
+                     (point)
+                     (progn (skip-chars-forward "0-9")
+                            (point)))))))
+           ;; Decide if we're switching buffers.
+           (buffer
+            (if (consp current-prefix-arg)
+                (other-buffer (current-buffer) t)))
+           (buffer-prompt
+            (if buffer
+                (concat " in " (buffer-name buffer))
+              "")))
+      ;; Read the argument, offering that number (if any) as default.
+      (list (read-number (format "Goto%s line%s: "
+                                 (if (= (point-min) 1) ""
+                                   ;; In a narrowed buffer.
+                                   (if relative " relative" " absolute"))
+                                 buffer-prompt)
+                         (list default (line-number-at-pos))
+                         'goto-line-history)
+            buffer))))
+
+(defun goto-line (line &optional buffer relative)
   "Go to LINE, counting from line 1 at beginning of buffer.
 If called interactively, a numeric prefix argument specifies
 LINE; without a numeric prefix argument, read LINE from the
@@ -1241,6 +1273,13 @@ If optional argument BUFFER is non-nil, switch to that buffer and
 move to line LINE there.  If called interactively with \\[universal-argument]
 as argument, BUFFER is the most recently selected other buffer.
 
+If optional argument RELATIVE is non-nil, counting starts at the beginning
+of the accessible portion of the (potentially narrowed) buffer.
+
+If the variable `widen-automatically' is non-nil, cancel narrowing and
+leave all lines accessible.  If `widen-automatically' is nil, just move
+point to the edge of visible portion and don't change the buffer bounds.
+
 Prior to moving point, this function sets the mark (without
 activating it), unless Transient Mark mode is enabled and the
 mark is already active.
@@ -1252,32 +1291,7 @@ What you probably want instead is something like:
 If at all possible, an even better solution is to use char counts
 rather than line counts."
   (declare (interactive-only forward-line))
-  (interactive
-   (if (and current-prefix-arg (not (consp current-prefix-arg)))
-       (list (prefix-numeric-value current-prefix-arg))
-     ;; Look for a default, a number in the buffer at point.
-     (let* ((default
-              (save-excursion
-                (skip-chars-backward "0-9")
-                (if (looking-at "[0-9]")
-                    (string-to-number
-                     (buffer-substring-no-properties
-                      (point)
-                      (progn (skip-chars-forward "0-9")
-                             (point)))))))
-            ;; Decide if we're switching buffers.
-            (buffer
-             (if (consp current-prefix-arg)
-                 (other-buffer (current-buffer) t)))
-            (buffer-prompt
-             (if buffer
-                 (concat " in " (buffer-name buffer))
-               "")))
-       ;; Read the argument, offering that number (if any) as default.
-       (list (read-number (format "Goto line%s: " buffer-prompt)
-                          (list default (line-number-at-pos))
-                          'goto-line-history)
-             buffer))))
+  (interactive (goto-line-read-args))
   ;; Switch to the desired buffer, one way or another.
   (if buffer
       (let ((window (get-buffer-window buffer)))
@@ -1286,13 +1300,27 @@ rather than line counts."
   ;; Leave mark at previous position
   (or (region-active-p) (push-mark))
   ;; Move to the specified line number in that buffer.
-  (save-restriction
-    (widen)
+  (if (and (not relative) (not widen-automatically))
+      (save-restriction
+        (widen)
+        (goto-char (point-min))
+        (if (eq selective-display t)
+            (re-search-forward "[\n\C-m]" nil 'end (1- line))
+          (forward-line (1- line))))
+    (unless relative (widen))
     (goto-char (point-min))
     (if (eq selective-display t)
         (re-search-forward "[\n\C-m]" nil 'end (1- line))
       (forward-line (1- line)))))
 
+(defun goto-line-relative (line &optional buffer)
+  "Go to LINE, counting from line at (point-min).
+The line number is relative to the accessible portion of the narrowed
+buffer.  The argument BUFFER is the same as in the function `goto-line'."
+  (declare (interactive-only forward-line))
+  (interactive (goto-line-read-args t))
+  (goto-line line buffer t))
+
 (defun count-words-region (start end &optional arg)
   "Count the number of words in the region.
 If called interactively, print a message reporting the number of