i18n: Add function ngettext for pluralization.

* lisp/international/mule-cmds.el (ngettext): New function.
https://lists.gnu.org/archive/html/emacs-devel/2019-03/msg00586.html

* lisp/replace.el (flush-lines, how-many, occur-1, occur-engine)
(perform-replace): Use ngettext.

* lisp/progmodes/grep.el (grep-exit-message): Use ngettext.
(grep-mode-font-lock-keywords): Match both singular and plural form
of "matches".

4 files changed, 54 insertions, 23 deletions

diff --git a/etc/NEWS b/etc/NEWS
index cb485992b8d..bbba59c5490 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1364,6 +1364,11 @@ Now, such rx expressions generate an error.
 
 * Lisp Changes in Emacs 27.1
 
+** i18n (internationalization)
+
+*** ngettext can be used now to return the right plural form
+according to the given numeric value.
+
 +++
 ** inhibit-null-byte-detection is renamed to inhibit-nul-byte-detection
 
diff --git a/lisp/international/mule-cmds.el b/lisp/international/mule-cmds.el
index 5f87d899415..035932e395d 100644
--- a/lisp/international/mule-cmds.el
+++ b/lisp/international/mule-cmds.el
@@ -2798,6 +2798,20 @@ See also `locale-charset-language-names', `locale-language-names',
 		      'a4)))))))
   nil)
 
+;;; i18n (internationalization)
+
+(defun ngettext (msgid msgid_plural n)
+  "Return the plural form of the translation of the string.
+This function is similar to the `gettext' function as it finds the message
+catalogs in the same way.  But it takes two extra arguments.  The MSGID
+parameter must contain the singular form of the string to be converted.
+It is also used as the key for the search in the catalog.
+The MSGID_PLURAL parameter is the plural form.  The parameter N is used
+to determine the plural form.  If no message catalog is found MSGID is
+returned if N is equal to 1, otherwise MSGID_PLURAL."
+  (if (= n 1) msgid msgid_plural))
+
+
 ;;; Character property
 
 (put 'char-code-property-table 'char-table-extra-slots 5)
diff --git a/lisp/progmodes/grep.el b/lisp/progmodes/grep.el
index a5427dd8b7e..c0f47159c95 100644
--- a/lisp/progmodes/grep.el
+++ b/lisp/progmodes/grep.el
@@ -459,7 +459,7 @@ abbreviated part can also be toggled with
      ;; remove match from grep-regexp-alist before fontifying
      ("^Grep[/a-zA-Z]* started.*"
       (0 '(face nil compilation-message nil help-echo nil mouse-face nil) t))
-     ("^Grep[/a-zA-Z]* finished with \\(?:\\(\\(?:[0-9]+ \\)?matches found\\)\\|\\(no matches found\\)\\).*"
+     ("^Grep[/a-zA-Z]* finished with \\(?:\\(\\(?:[0-9]+ \\)?match\\(?:es\\)? found\\)\\|\\(no matches found\\)\\).*"
       (0 '(face nil compilation-message nil help-echo nil mouse-face nil) t)
       (1 compilation-info-face nil t)
       (2 compilation-warning-face nil t))
@@ -552,7 +552,10 @@ Set up `compilation-exit-message-function' and run `grep-setup-hook'."
       ;; so the buffer is still unmodified if there is no output.
       (cond ((and (zerop code) (buffer-modified-p))
 	     (if (> grep-num-matches-found 0)
-                 (cons (format "finished with %d matches found\n" grep-num-matches-found)
+                 (cons (format (ngettext "finished with %d match found\n"
+                                         "finished with %d matches found\n"
+                                         grep-num-matches-found)
+                               grep-num-matches-found)
                        "matched")
                '("finished with matches found\n" . "matched")))
 	    ((not (buffer-modified-p))
diff --git a/lisp/replace.el b/lisp/replace.el
index 59ad1a375b8..318a9fb0253 100644
--- a/lisp/replace.el
+++ b/lisp/replace.el
@@ -983,7 +983,10 @@ also print the number."
 		       (progn (forward-line 1) (point)))
         (setq count (1+ count))))
     (set-marker rend nil)
-    (when interactive (message "Deleted %d matching lines" count))
+    (when interactive (message (ngettext "Deleted %d matching line"
+					 "Deleted %d matching lines"
+					 count)
+			       count))
     count))
 
 (defun how-many (regexp &optional rstart rend interactive)
@@ -1032,9 +1035,10 @@ a previously found match."
 	(if (= opoint (point))
 	    (forward-char 1)
 	  (setq count (1+ count))))
-      (when interactive (message "%d occurrence%s"
-				 count
-				 (if (= count 1) "" "s")))
+      (when interactive (message (ngettext "%d occurrence"
+					   "%d occurrences"
+					   count)
+				 count))
       count)))
 
 
@@ -1617,11 +1621,12 @@ See also `multi-occur'."
 		  (not (eq occur-excluded-properties t))))))
 	  (let* ((bufcount (length active-bufs))
 		 (diff (- (length bufs) bufcount)))
-	    (message "Searched %d buffer%s%s; %s match%s%s"
-		     bufcount (if (= bufcount 1) "" "s")
+	    (message "Searched %d %s%s; %s %s%s"
+		     bufcount
+		     (ngettext "buffer" "buffers" bufcount)
 		     (if (zerop diff) "" (format " (%d killed)" diff))
 		     (if (zerop count) "no" (format "%d" count))
-		     (if (= count 1) "" "es")
+		     (ngettext "match" "matches" count)
 		     ;; Don't display regexp if with remaining text
 		     ;; it is longer than window-width.
 		     (if (> (+ (length (or (get-text-property 0 'isearch-string regexp)
@@ -1856,14 +1861,15 @@ See also `multi-occur'."
 		  (let ((beg (point))
 		        end)
 		    (insert (propertize
-			     (format "%d match%s%s%s in buffer: %s%s\n"
-				     matches (if (= matches 1) "" "es")
+			     (format "%d %s%s%s in buffer: %s%s\n"
+				     matches
+				     (ngettext "match" "matches" matches)
 				     ;; Don't display the same number of lines
 				     ;; and matches in case of 1 match per line.
 				     (if (= lines matches)
-				         "" (format " in %d line%s"
+				         "" (format " in %d %s"
 						    lines
-						    (if (= lines 1) "" "s")))
+						    (ngettext "line" "lines" lines)))
 				     ;; Don't display regexp for multi-buffer.
 				     (if (> (length buffers) 1)
 				         "" (occur-regexp-descr regexp))
@@ -1889,13 +1895,15 @@ See also `multi-occur'."
 	(goto-char (point-min))
 	(let ((beg (point))
 	      end)
-	  (insert (format "%d match%s%s total%s:\n"
-			  global-matches (if (= global-matches 1) "" "es")
+	  (insert (format "%d %s%s total%s:\n"
+			  global-matches
+			  (ngettext "match" "matches" global-matches)
 			  ;; Don't display the same number of lines
 			  ;; and matches in case of 1 match per line.
 			  (if (= global-lines global-matches)
-			      "" (format " in %d line%s"
-					 global-lines (if (= global-lines 1) "" "s")))
+			      "" (format " in %d %s"
+					 global-lines
+					 (ngettext "line" "lines" global-lines)))
 			  (occur-regexp-descr regexp)))
 	  (setq end (point))
 	  (when title-face
@@ -2730,10 +2738,10 @@ characters."
                                            (1+ num-replacements))))))
                              (when (and (eq def 'undo-all)
                                         (null (zerop num-replacements)))
-                               (message "Undid %d %s" num-replacements
-                                        (if (= num-replacements 1)
-                                            "replacement"
-                                          "replacements"))
+                               (message (ngettext "Undid %d replacement"
+                                                  "Undid %d replacements"
+                                                  num-replacements)
+                                        num-replacements)
                                (ding 'no-terminate)
                                (sit-for 1)))
 			   (setq replaced nil last-was-undo t last-was-act-and-show nil)))
@@ -2859,9 +2867,10 @@ characters."
                       last-was-act-and-show     nil))))))
       (replace-dehighlight))
     (or unread-command-events
-	(message "Replaced %d occurrence%s%s"
+	(message (ngettext "Replaced %d occurrence%s"
+			   "Replaced %d occurrences%s"
+			   replace-count)
 		 replace-count
-		 (if (= replace-count 1) "" "s")
 		 (if (> (+ skip-read-only-count
 			   skip-filtered-count
 			   skip-invisible-count)