Make info-xref checks case-sensitive by default

* lisp/info.el (Info-find-node, Info-find-in-tag-table)
(Info-find-node-in-buffer, Info-find-node-2, Info-goto-node):
Add option for exact case matching of nodes.

* lisp/info-xref.el (info-xref): New custom group.
(info-xref-case-fold): New option.
(info-xref-goto-node-p): Pass info-xref-case-fold to Info-goto-node.

3 files changed, 58 insertions, 18 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index f717fdcc4e4..8327fb03b4e 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,13 @@
+2013-07-03  Glenn Morris  <rgm@gnu.org>
+
+        Make info-xref checks case-sensitive by default
+        * info.el (Info-find-node, Info-find-in-tag-table)
+        (Info-find-node-in-buffer, Info-find-node-2, Info-goto-node):
+        Add option for exact case matching of nodes.
+        * info-xref.el (info-xref): New custom group.
+        (info-xref-case-fold): New option.
+        (info-xref-goto-node-p): Pass info-xref-case-fold to Info-goto-node.
+
 2013-07-03  Leo Liu  <sdl.web@gmail.com>
 
         * ido.el (ido-delete-file-at-head): Respect delete-by-moving-to-trash.
diff --git a/lisp/info-xref.el b/lisp/info-xref.el
index c38e23bab8a..21fb592ff19 100644
--- a/lisp/info-xref.el
+++ b/lisp/info-xref.el
@@ -45,7 +45,25 @@
 ;;; Code:
 
 (require 'info)
-(eval-when-compile (require 'cl-lib)) ;; for `incf'
+(eval-when-compile (require 'cl-lib))   ; for `cl-incf'
+
+(defgroup info-xref nil
+  "Check external cross-references in Info documents."
+  :group 'docs)                         ; FIXME right parent?
+
+;; Should this even be an option?
+(defcustom info-xref-case-fold nil
+  "Non-nil means node checks should ignore case.
+When following cross-references, the Emacs Info reader first tries a
+case-sensitive match, then if that fails a case-insensitive one.
+The standalone Info reader does not do this, nor does this work
+for links in the html versions of Texinfo manuals.  Therefore
+to ensure your cross-references work on the widest range of platforms,
+you should set this variable to nil."
+  :group 'info-xref
+  :type 'boolean
+  :version "24.4")
+
 
 ;;-----------------------------------------------------------------------------
 ;; vaguely generic
@@ -204,7 +222,8 @@ buffer's line and column of point."
                   (Info-goto-node node
                                   (when (get-buffer "*info*")
                                     (set-buffer "*info*")
-                                    "xref - temporary"))
+                                    "xref - temporary")
+                                  (not info-xref-case-fold))
                   t)
               (error nil))
           (unless (equal (current-buffer) oldbuf)
diff --git a/lisp/info.el b/lisp/info.el
index f9851a0c1e8..0e0a11753ba 100644
--- a/lisp/info.el
+++ b/lisp/info.el
@@ -920,10 +920,14 @@ just return nil (no error)."
           (error "Info file %s does not exist" filename)))
       filename))))
 
-(defun Info-find-node (filename nodename &optional no-going-back)
+(defun Info-find-node (filename nodename &optional no-going-back strict-case)
   "Go to an Info node specified as separate FILENAME and NODENAME.
 NO-GOING-BACK is non-nil if recovering from an error in this function;
-it says do not attempt further (recursive) error recovery."
+it says do not attempt further (recursive) error recovery.
+
+This function first looks for a case-sensitive match for NODENAME;
+if none is found it then tries a case-insensitive match (unless
+STRICT-CASE is non-nil)."
   (info-initialize)
   (setq filename (Info-find-file filename))
   ;; Go into Info buffer.
@@ -933,7 +937,7 @@ it says do not attempt further (recursive) error recovery."
        Info-current-file
        (push (list Info-current-file Info-current-node (point))
              Info-history))
-  (Info-find-node-2 filename nodename no-going-back))
+  (Info-find-node-2 filename nodename no-going-back strict-case))
 
 ;;;###autoload
 (defun Info-on-current-buffer (&optional nodename)
@@ -1010,7 +1014,7 @@ which the match was found."
               (+ (point-min) (read (current-buffer)))
               major-mode)))))
 
-(defun Info-find-in-tag-table (marker regexp)
+(defun Info-find-in-tag-table (marker regexp &optional strict-case)
   "Find a node in a tag table.
 MARKER specifies the buffer and position to start searching at.
 REGEXP is a regular expression matching nodes or references.  Its first
@@ -1020,10 +1024,11 @@ FOUND-ANCHOR is non-nil if a `Ref:' was matched, POS is the position
 where the match was found, and MODE is `major-mode' of the buffer in
 which the match was found.
 This function tries to find a case-sensitive match first, then a
-case-insensitive match is tried."
+case-insensitive match is tried (unless optional argument STRICT-CASE
+is non-nil)."
   (let ((result (Info-find-in-tag-table-1 marker regexp nil)))
-    (when (null (car result))
-      (setq result (Info-find-in-tag-table-1 marker regexp t)))
+    (or strict-case (car result)
+        (setq result (Info-find-in-tag-table-1 marker regexp t)))
     result))
 
 (defun Info-find-node-in-buffer-1 (regexp case-fold)
@@ -1046,17 +1051,19 @@ Value is the position at which a match was found, or nil if not found."
                 (setq found (line-beginning-position)))))))
     found))
 
-(defun Info-find-node-in-buffer (regexp)
+(defun Info-find-node-in-buffer (regexp &optional strict-case)
   "Find a node or anchor in the current buffer.
 REGEXP is a regular expression matching nodes or references.  Its first
 group should match `Node:' or `Ref:'.
 Value is the position at which a match was found, or nil if not found.
 This function looks for a case-sensitive match first.  If none is found,
-a case-insensitive match is tried."
+a case-insensitive match is tried (unless optional argument STRICT-CASE
+is non-nil)."
   (or (Info-find-node-in-buffer-1 regexp nil)
-      (Info-find-node-in-buffer-1 regexp t)))
+      (and (not strict-case)
+           (Info-find-node-in-buffer-1 regexp t))))
 
-(defun Info-find-node-2 (filename nodename &optional no-going-back)
+(defun Info-find-node-2 (filename nodename &optional no-going-back strict-case)
   (buffer-disable-undo (current-buffer))
   (or (eq major-mode 'Info-mode)
       (Info-mode))
@@ -1167,7 +1174,7 @@ a case-insensitive match is tried."
               ;; First, search a tag table, if any
               (when (marker-position Info-tag-table-marker)
                 (let* ((m Info-tag-table-marker)
-                       (found (Info-find-in-tag-table m regexp)))
+                       (found (Info-find-in-tag-table m regexp strict-case)))
 
                   (when found
                     ;; FOUND is (ANCHOR POS MODE).
@@ -1194,7 +1201,7 @@ a case-insensitive match is tried."
               ;; buffer) to find the actual node.  First, check
               ;; whether the node is right where we are, in case the
               ;; buffer begins with a node.
-              (let ((pos (Info-find-node-in-buffer regexp)))
+              (let ((pos (Info-find-node-in-buffer regexp strict-case)))
                 (when pos
                   (goto-char pos)
                   (throw 'foo t)))
@@ -1701,7 +1708,7 @@ escaped (\\\",\\\\)."
 ;; Don't autoload this function: the correct entry point for other packages
 ;; to use is `info'.  --Stef
 ;; ;;;###autoload
-(defun Info-goto-node (nodename &optional fork)
+(defun Info-goto-node (nodename &optional fork strict-case)
   "Go to Info node named NODENAME.  Give just NODENAME or (FILENAME)NODENAME.
 If NODENAME is of the form (FILENAME)NODENAME, the node is in the Info file
 FILENAME; otherwise, NODENAME should be in the current Info file (or one of
@@ -1711,7 +1718,11 @@ in the Info file FILENAME after the closing parenthesis in (FILENAME).
 Empty NODENAME in (FILENAME) defaults to the Top node.
 If FORK is non-nil (interactively with a prefix arg), show the node in
 a new Info buffer.
-If FORK is a string, it is the name to use for the new buffer."
+If FORK is a string, it is the name to use for the new buffer.
+
+This function first looks for a case-sensitive match for the node part
+of NODENAME; if none is found it then tries a case-insensitive match
+\(unless STRICT-CASE is non-nil)."
   (interactive (list (Info-read-node-name "Go to node: ") current-prefix-arg))
   (info-initialize)
   (if fork
@@ -1730,7 +1741,7 @@ If FORK is a string, it is the name to use for the new buffer."
       (if trim (setq nodename (substring nodename 0 trim))))
     (if transient-mark-mode (deactivate-mark))
     (Info-find-node (if (equal filename "") nil filename)
-                    (if (equal nodename "") "Top" nodename))))
+                    (if (equal nodename "") "Top" nodename) nil strict-case)))
 
 (defvar Info-read-node-completion-table)