bug#23050: package.el overwrites symlinks when saving "(package-initialize)"

[Paul Eggert <eggert@cs.ucla.edu>]

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> So package.el could avoid the issue by binding
> find-file-visit-truename, like cus-edit does (see bug#454).

Thanks, that suggestion worked when I tried it, so I installed the attached 
patch into emacs-25 and am marking this bug as done.

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From 239521765c6ecf5679463dd9603359bf907570eb Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Sun, 22 May 2016 17:29:58 -0700
Subject: [PATCH] Do not trash symlinks to init file
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

If the user’s init file is a symbolic link, do not break the link
when initializing the package system.  Problem reported by Jackson
Hamilton (Bug#23050).
* lisp/emacs-lisp/package.el (package--ensure-init-file):
Bind find-file-visit-truename when visiting the init file, and
save and restore the buffer name the way cus-edit does in a
similar situation (Bug#454).
---
 lisp/emacs-lisp/package.el | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/lisp/emacs-lisp/package.el b/lisp/emacs-lisp/package.el
index b0a6db0..14626e2 100644
--- a/lisp/emacs-lisp/package.el
+++ b/lisp/emacs-lisp/package.el
@@ -1869,6 +1869,7 @@ package--ensure-init-file
              (file-readable-p user-init-file)
              (file-writable-p user-init-file))
     (let* ((buffer (find-buffer-visiting user-init-file))
+           buffer-name
            (contains-init
             (if buffer
                 (with-current-buffer buffer
@@ -1884,8 +1885,12 @@ package--ensure-init-file
                 (re-search-forward "(package-initialize\\_>" nil 'noerror)))))
       (unless contains-init
         (with-current-buffer (or buffer
-                                 (let ((delay-mode-hooks t))
+                                 (let ((delay-mode-hooks t)
+                                       (find-file-visit-truename t))
                                    (find-file-noselect user-init-file)))
+          (when buffer
+            (setq buffer-name (buffer-file-name))
+            (set-visited-file-name (file-chase-links user-init-file)))
           (save-excursion
             (save-restriction
               (widen)
@@ -1904,7 +1909,10 @@ package--ensure-init-file
                 (insert "\n"))
               (let ((file-precious-flag t))
                 (save-buffer))
-              (unless buffer
+              (if buffer
+                  (progn
+                    (set-visited-file-name buffer-name)
+                    (set-buffer-modified-p nil))
                 (kill-buffer (current-buffer)))))))))
   (setq package--init-file-ensured t))
 
-- 
2.7.4