bug#15201: 24.2; extensions/enhancements to package.el

[Ryan Davis]

I know that using cl is frowned upon... but I'm writing this code to be
compatible with 24.2 so I can't rely on cl-lib (since this is an
extension to the system used to install cl-lib). I'm only using it for
set-difference and am open to modifications to make it more
portable/acceptable. You can see this code in:

https://github.com/zenspider/package/blob/master/package%2B.el#L70-L104

  (require 'cl)

  (defun package-version-for (name)
    "Returns the installed version for a package with a given NAME."
    (package-desc-vers (cdr (assoc name package-alist))))

  (defun package-delete-by-name (name)
    "Deletes a package by NAME"
    (message "Removing %s" name)
    (package-delete (symbol-name name)
                    (package-version-join (package-version-for name))))

  (defun package-maybe-install (name)
    "Installs a package by NAME, but only if it isn't already installed."
    (unless (package-installed-p name)
      (message "Installing %s" name)
      (package-install name)))

  (defun package-deps-for (pkg)
    "Returns the dependency list for PKG or nil if none or the PKG doesn't 
exist."
    (let ((v (cdr (assoc pkg package-alist))))
      (and v (package-desc-reqs v))))

  (defun package-transitive-closure (pkgs)
    (let ((deps '()))
      (dolist (pkg pkgs deps)
        (add-to-list 'deps pkg)
        (dolist (new-pkg (mapcar 'car (package-deps-for pkg)))
          (add-to-list 'deps new-pkg)))))

  (defun package-cleanup (packages)
    "Delete installed packages not explicitly declared in PACKAGES."
    (let ((removes (set-difference (mapcar 'car package-alist)
                                   (package-transitive-closure packages))))
      (mapc 'package-delete-by-name removes)))

;;; finis

In GNU Emacs 24.2.1 (x86_64-apple-darwin12.2.0, NS apple-appkit-1187.34)
of 2012-09-20 on greed.local
Windowing system distributor `Apple', version 10.3.1187
Configured using:
`configure '--prefix=/usr/local/Cellar/emacs/24.2' '--without-dbus'
'--enable-locallisppath=/usr/local/share/emacs/site-lisp'
'--infodir=/usr/local/Cellar/emacs/24.2/share/info/emacs' '--with-ns'
'--disable-ns-self-contained''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: nil
  value of $XMODIFIERS: nil
  locale-coding-system: nil
  default enable-multibyte-characters: t

Major mode: Fundamental

Minor modes in effect:
  tooltip-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
s-x <escape> x r e p <tab> o <tab> r <tab> <return
>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
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