* lisp/emacs-lisp/package.el: Make archive and status pseudo-keywords

(package--has-keyword-p): Understand "arc:xxxx" and "status:xxxx"
as special keywords which match agains package archive and status
respectively.

* etc/NEWS: Document it.

etc/NEWS

@@ -238,6 +238,11 @@ in the surrounding GUI (using the OSC-52 escape sequence).
 ** xterm-mouse-mode now supports mouse-tracking (if your xterm supports it).
 
 ** package.el
+
+*** When filtering the package menu, keywords starting with "arc:" or
+"status:" represent package archive or status, respectively, instead
+of actual keywords.
+
 *** Most functions which involve downloading information now take an
 ASYNC argument.  If it is non-nil, package.el performs the download(s)
 asynchronously.

lisp/emacs-lisp/package.el

@@ -2535,12 +2535,14 @@ Built-in packages are converted with `package--from-builtin'."
   "Test if package DESC has any of the given KEYWORDS.
 When none are given, the package matches."
   (if keywords
-      (let* ((desc-keywords (and desc (package-desc--keywords desc)))
-             found)
-        (dolist (k keywords)
-          (when (and (not found)
-                     (member k desc-keywords))
-            (setq found t)))
+      (let ((desc-keywords (and desc (package-desc--keywords desc)))
+            found)
+        (while (and (not found) keywords)
+          (let ((k (pop keywords)))
+            (setq found
+                  (or (string= k (concat "arc:" (package-desc-archive desc)))
+                      (string= k (concat "status:" (package-desc-status desc)))
+                      (member k desc-keywords)))))
         found)
     t))