From 7d5856bd4570a6c5a3cf1daf6273b638e09b6d50 Mon Sep 17 00:00:00 2001
From: Tim Gesthuizen <tim.gesthuizen@yahoo.de>
Date: Fri, 4 Jan 2019 22:34:36 +0100
Subject: gnu: Add package-elisp-from-package

Add a function to generate package definitions that packages single elisp
files from other packages.

* gnu/packages/emacs.scm (package-elisp-from-package): New function
---
 gnu/packages/emacs.scm | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/gnu/packages/emacs.scm b/gnu/packages/emacs.scm
index ec67f278c9..cbfec8f70a 100644
--- a/gnu/packages/emacs.scm
+++ b/gnu/packages/emacs.scm
@@ -35,7 +35,7 @@
 ;;; Copyright © 2018 Sohom Bhattacharjee <soham.bhattacharjee15@gmail.com>
 ;;; Copyright © 2018 Mathieu Lirzin <mthl@gnu.org>
 ;;; Copyright © 2018 Pierre Neidhardt <mail@ambrevar.xyz>
-;;; Copyright © 2018 Tim Gesthuizen <tim.gesthuizen@yahoo.de>
+;;; Copyright © 2018, 2019 Tim Gesthuizen <tim.gesthuizen@yahoo.de>
 ;;; Copyright © 2018 Jack Hill <jackhill@jackhill.us>
 ;;; Copyright © 2018 Pierre-Antoine Rouby <pierre-antoine.rouby@inria.fr>
 ;;; Copyright © 2018 Alex Branham <alex.branham@gmail.com>
@@ -331,6 +331,36 @@ editor (without an X toolkit)" )
              (lambda _
                (invoke "mkdir" "-p" "src/deps")))))))))
 
+(define-public (package-elisp-from-package
+                source-package package-name source-files)
+  "Returns a package definition that packages emacs-lisp files from the
+SOURCE-PACKAGEs source.  The package has the name PACKAGE-NAME and packages
+the files SOURCE-FILES from the source in its root directory."
+  (let ((orig (package-source source-package)))
+    (package
+      (inherit source-package)
+      (name package-name)
+      (build-system emacs-build-system)
+      (source (origin
+                (method (origin-method orig))
+                (uri (origin-uri orig))
+                (sha256 (origin-sha256 orig))
+                (file-name (string-append package-name "-"
+                                          (package-version source-package)))
+                (modules '((guix build utils)
+                           (srfi srfi-1)
+                           (ice-9 ftw)))
+                (snippet
+                 `(let* ((source-files (quote ,source-files))
+                         (basenames (map basename source-files)))
+                    (map copy-file
+                         source-files basenames)
+                    (map delete-file-recursively
+                         (fold delete
+                               (scandir ".")
+                               (append '("." "..") basenames)))
+                    #t)))))))
+
 
 ;;;
 ;;; Emacs hacking.
-- 
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