bug#19481: package.el: support .tar archives featuring a pax_global_header entry

[Ivan Shmakov]

Package:  emacs
Severity: minor

        As currently implemented, package.el signals an error trying to
        process a .tar archive which has a pax_global_header entry, –
        such as the archives produced with $ git archive --format=tar.

        Please thus consider the patch MIMEd.

        * lisp/emacs-lisp/package.el (package-untar-buffer): Ignore
        archive entries with link type being 55.
        (package-tar-file-info): Consider the second file name in the
        archive if the first one has no directory component.

        * lisp/tar-mode.el (tar-untar-buffer): Ignore archive entries
        with link type being 55 (pax global extended header.)

-- 
FSF associate member #7257  http://boycottsystemd.org/  … 3013 B6A0 230E 334A

--- a/lisp/emacs-lisp/package.el
+++ b/lisp/emacs-lisp/package.el
@@ -739,6 +739,8 @@ defun package-untar-buffer (dir)
     (dolist (tar-data tar-parse-info)
       (let ((name (expand-file-name (tar-header-name tar-data))))
        (or (string-match regexp name)
+           ;; Ignore the pax_global_header entry.
+           (eq 55 (tar-header-link-type tar-data))
            ;; Tarballs created by some utilities don't list
            ;; directories with a trailing slash (Bug#13136).
            (and (string-equal dir name)
@@ -1245,8 +1247,10 @@ defun package-tar-file-info ()
   "Find package information for a tar file.
 The return result is a `package-desc'."
   (cl-assert (derived-mode-p 'tar-mode))
-  (let* ((dir-name (file-name-directory
-                    (tar-header-name (car tar-parse-info))))
+  (let* ((dir-name
+         ;; Take care of pax_global_header, if any.
+         (or (file-name-directory (tar-header-name (car  tar-parse-info)))
+             (file-name-directory (tar-header-name (cadr tar-parse-info)))))
          (desc-file (package--description-file dir-name))
          (tar-desc (tar-get-file-descriptor (concat dir-name desc-file))))
     (unless tar-desc
--- a/lisp/tar-mode.el
+++ b/lisp/tar-mode.el
@@ -479,10 +550,12 @@ defun tar-untar-buffer ()
             (message "Extracting %s" name)
             (if (and dir (not (file-exists-p dir)))
                 (make-directory dir t))
-            (unless (file-directory-p name)
-             (let ((coding-system-for-write 'no-conversion))
-               (write-region start end name)))
-            (set-file-modes name (tar-header-mode descriptor))))))))
+           ;; Ignore the pax_global_header entry.
+           (unless (eq 55 (tar-header-link-type descriptor))
+             (unless (or (file-directory-p name))
+               (let ((coding-system-for-write 'no-conversion))
+                 (write-region start end name)))
+             (set-file-modes name (tar-header-mode descriptor)))))))))
 
 (defun tar-summarize-buffer ()
   "Parse the contents of the tar file in the current buffer."