Make pcomplete-ignore-case obsolete

* lisp/pcomplete.el (pcomplete-completions-at-point)
(pcomplete-stub, pcomplete--entries, pcomplete-insert-entry):
* lisp/eshell/em-cmpl.el (eshell-cmpl-initialize):
* lisp/eshell/em-cmpl.el (eshell-cmpl-ignore-case):
* lisp/erc/erc-pcomplete.el (pcomplete-erc-setup): Use
`completion-ignore-case' instead (bug#23117).

* lisp/pcomplete.el (pcomplete-ignore-case): Make obsolete.

etc/NEWS

@@ -2056,6 +2056,8 @@ directory instead of the default directory.
 
 * Incompatible Lisp Changes in Emacs 28.1
 
+** 'pcomplete-ignore-case' is now an obsolete alias of 'completion-ignore-case'.
+
 ** 'completions-annotations' face is not used when the caller puts own face.
 This affects the suffix specified by completion 'annotation-function'.
 

lisp/erc/erc-pcomplete.el

@@ -89,7 +89,7 @@ for use on `completion-at-point-function'."
 
 (defun pcomplete-erc-setup ()
   "Setup `erc-mode' to use pcomplete."
-  (setq-local pcomplete-ignore-case t)
+  (setq-local completion-ignore-case t)
   (setq-local pcomplete-use-paring nil)
   (setq-local pcomplete-parse-arguments-function
               #'pcomplete-erc-parse-arguments)

lisp/eshell/em-cmpl.el

@@ -150,8 +150,8 @@ to writing a completion function."
   :type (get 'pcomplete-dir-ignore 'custom-type))
 
 (defcustom eshell-cmpl-ignore-case (eshell-under-windows-p)
-  (eshell-cmpl--custom-variable-docstring 'pcomplete-ignore-case)
-  :type (get 'pcomplete-ignore-case 'custom-type))
+  (eshell-cmpl--custom-variable-docstring 'completion-ignore-case)
+  :type (get 'completion-ignore-case 'custom-type))
 
 (defcustom eshell-cmpl-autolist nil
   (eshell-cmpl--custom-variable-docstring 'pcomplete-autolist)
@@ -259,7 +259,7 @@ to writing a completion function."
               eshell-cmpl-file-ignore)
   (setq-local pcomplete-dir-ignore
               eshell-cmpl-dir-ignore)
-  (setq-local pcomplete-ignore-case
+  (setq-local completion-ignore-case
               eshell-cmpl-ignore-case)
   (setq-local pcomplete-autolist
               eshell-cmpl-autolist)

lisp/pcomplete.el

@@ -135,11 +135,8 @@
   "A regexp of names to be disregarded during directory completion."
   :type '(choice regexp (const :tag "None" nil)))
 
-(defcustom pcomplete-ignore-case (memq system-type '(ms-dos windows-nt cygwin))
-  ;; FIXME: the doc mentions file-name completion, but the code
-  ;; seems to apply it to all completions.
-  "If non-nil, ignore case when doing filename completion."
-  :type 'boolean)
+(define-obsolete-variable-alias 'pcomplete-ignore-case 'completion-ignore-case
+  "28.1")
 
 (defcustom pcomplete-autolist nil
   "If non-nil, automatically list possibilities on partial completion.
@@ -472,7 +469,7 @@ Same as `pcomplete' but using the standard completion UI."
                      (not (member
                            (funcall norm-func (directory-file-name f))
                            seen)))))))
-          (when pcomplete-ignore-case
+          (when completion-ignore-case
             (setq table (completion-table-case-fold table)))
           (list beg (point) table
                 :predicate pred
@@ -865,7 +862,7 @@ this is `comint-dynamic-complete-functions'."
                            (sort comps pcomplete-compare-entry-function)))
                      ,@(cdr (completion-file-name-table s p a)))
         (let ((completion-ignored-extensions nil)
-	      (completion-ignore-case pcomplete-ignore-case))
+	      (completion-ignore-case completion-ignore-case))
           (completion-table-with-predicate
            #'comint-completion-file-name-table pred 'strict s p a))))))
 
@@ -1116,7 +1113,7 @@ Typing SPC flushes the help buffer."
   "Insert a completion entry at point.
 Returns non-nil if a space was appended at the end."
   (let ((here (point)))
-    (if (not pcomplete-ignore-case)
+    (if (not completion-ignore-case)
 	(insert-and-inherit (if raw-p
 				(substring entry (length stub))
 			      (comint-quote-filename
@@ -1194,7 +1191,7 @@ Returns `partial' if completed as far as possible with the matches.
 Returns `listed' if a completion listing was shown.
 
 See also `pcomplete-filename'."
-  (let* ((completion-ignore-case pcomplete-ignore-case)
+  (let* ((completion-ignore-case completion-ignore-case)
 	 (completions (all-completions stub candidates))
          (entry (try-completion stub candidates))
          result)