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diff --git a/lisp/package/package-quickstart.el b/lisp/package/package-quickstart.el
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+;;; package-quickstart.el --- Accelerating Package Startup -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2025  Philip Kaludercic
+
+;; Author: Philip Kaludercic <philipk@posteo.net>
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; Activating packages via `package-initialize' is costly: for N installed
+;; packages, it needs to read all N <pkg>-pkg.el files first to decide
+;; which packages to activate, and then again N <pkg>-autoloads.el files.
+;; To speed this up, we precompute a mega-autoloads file which is the
+;; concatenation of all those <pkg>-autoloads.el, so we can activate
+;; all packages by loading this one file (and hence without initializing
+;; package.el).
+
+;; Other than speeding things up, this also offers a bootstrap feature:
+;; it lets us activate packages according to `package-load-list' and
+;; `package-user-dir' even before those vars are set.
+
+;;; Code:
+
+(require 'package-core)
+
+(defcustom package-quickstart nil
+  "Precompute activation actions to speed up startup.
+This requires the use of `package-quickstart-refresh' every time the
+activations need to be changed, such as when `package-load-list' is modified."
+  :type 'boolean
+  :version "27.1"
+  :group 'package)
+
+;;;###autoload
+(defcustom package-quickstart-file
+  (locate-user-emacs-file "package-quickstart.el")
+  "Location of the file used to speed up activation of packages at startup."
+  :type 'file
+  :group 'applications
+  :initialize #'custom-initialize-delay
+  :version "27.1")
+
+(defun package--quickstart-maybe-refresh ()
+  (if package-quickstart
+      ;; FIXME: Delay refresh in case we're installing/deleting
+      ;; several packages!
+      (package-quickstart-refresh)
+    (delete-file (concat package-quickstart-file "c"))
+    (delete-file package-quickstart-file)))
+
+(defvar package--quickstart-dir nil
+  "Set by `package-quickstart-file' to the directory containing it.")
+
+(defun package--quickstart-rel (file)
+  "Return an expr depending on `package--quickstart-dir' which evaluates to FILE.
+
+If FILE is in `package--quickstart-dir', returns an expression that is
+relative to that directory, so if that directory is moved we can still
+find FILE."
+  (if (file-in-directory-p file package--quickstart-dir)
+      `(file-name-concat package--quickstart-dir ,(file-relative-name file package--quickstart-dir))
+    file))
+
+(defun package-quickstart-refresh ()
+  "(Re)Generate the `package-quickstart-file'."
+  (interactive)
+  (package-initialize 'no-activate)
+  (require 'info)
+  (let ((package--quickstart-pkgs ())
+        ;; Pretend we haven't activated anything yet!
+        (package-activated-list ())
+        ;; Make sure we can load this file without load-source-file-function.
+        (coding-system-for-write 'emacs-internal)
+        ;; Ensure that `pp' and `prin1-to-string' calls further down
+        ;; aren't truncated.
+        (print-length nil)
+        (print-level nil)
+        (Info-directory-list '(""))
+        (package--quickstart-dir nil))
+    (dolist (elt package-alist)
+      (condition-case err
+          (package-activate (car elt))
+        ;; Don't let failure of activation of a package arbitrarily stop
+        ;; activation of further packages.
+        (error (message "%s" (error-message-string err)))))
+    (setq package--quickstart-pkgs (nreverse package--quickstart-pkgs))
+    (with-temp-file package-quickstart-file
+      (emacs-lisp-mode)                 ;For `syntax-ppss'.
+      (insert ";;; Quickstart file to activate all packages at startup  -*- lexical-binding:t -*-\n")
+      (insert ";; ¡¡ This file is autogenerated by `package-quickstart-refresh', DO NOT EDIT !!\n\n")
+      (setq package--quickstart-dir
+            (file-name-directory (expand-file-name package-quickstart-file)))
+      (pp '(setq package--quickstart-dir
+                 (file-name-directory (expand-file-name load-file-name)))
+          (current-buffer))
+      (dolist (pkg package--quickstart-pkgs)
+        (let* ((file
+                ;; Prefer uncompiled files (and don't accept .so files).
+                (let ((load-suffixes '(".el" ".elc")))
+                  (locate-library (package--autoloads-file-name pkg))))
+               (pfile (prin1-to-string (package--quickstart-rel file))))
+          (insert "(let* ((load-file-name " pfile ")\
+\(load-true-file-name load-file-name))\n")
+          (insert-file-contents file)
+          ;; Fixup the special #$ reader form and throw away comments.
+          (while (re-search-forward "#\\$\\|^;\\(.*\n\\)" nil 'move)
+            (unless (ppss-string-terminator (save-match-data (syntax-ppss)))
+              (replace-match (if (match-end 1) "" pfile) t t)))
+          (unless (bolp) (insert "\n"))
+          (insert ")\n")))
+      (pp `(defvar package-activated-list) (current-buffer))
+      (pp `(setq package-activated-list
+                 (delete-dups
+                  (append ',(mapcar #'package-desc-name package--quickstart-pkgs)
+                          package-activated-list)))
+          (current-buffer))
+      (let ((info-dirs
+             (mapcar #'package--quickstart-rel (butlast Info-directory-list))))
+        (when info-dirs
+          (pp `(progn (require 'info)
+                      (info-initialize)
+                      (setq Info-directory-list
+                            (append (list . ,info-dirs) Info-directory-list)))
+              (current-buffer))))
+      ;; Use `\s' instead of a space character, so this code chunk is not
+      ;; mistaken for an actual file-local section of package.el.
+      (insert "
+;; Local\sVariables:
+;; version-control: never
+;; no-update-autoloads: t
+;; byte-compile-warnings: (not make-local)
+;; End:
+"))
+    ;; FIXME: Do it asynchronously in an Emacs subprocess, and
+    ;; don't show the byte-compiler warnings.
+    (byte-compile-file package-quickstart-file)))
+
+(provide 'package-quickstart)
+;;; package-quickstart.el ends here