gnu: Add emacs-ag.

* gnu/packages/emacs.scm (emacs-ag): New variable.

Signed-off-by: Alex Kost <alezost@gmail.com>

gnu/packages/emacs.scm

@@ -17,6 +17,7 @@
 ;;; Copyright © 2016 Nicolas Goaziou <mail@nicolasgoaziou.fr>
 ;;; Copyright © 2016 Alex Vong <alexvong1995@gmail.com>
 ;;; Copyright © 2016 Arun Isaac <arunisaac@systemreboot.net>
+;;; Copyright © 2017 Christopher Baines <mail@cbaines.net>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -46,6 +47,7 @@ (define-module (gnu packages emacs)
   #:use-module (guix build-system glib-or-gtk)
   #:use-module (guix build-system trivial)
   #:use-module (gnu packages)
+  #:use-module (gnu packages code)
   #:use-module (gnu packages guile)
   #:use-module (gnu packages gtk)
   #:use-module (gnu packages gnome)
@@ -1066,6 +1068,44 @@ (define-public bbdb
 mode, Rmail, Gnus, MH-E, and VM).  BBDB is fully customizable.")
     (license license:gpl3+)))
 
+(define-public emacs-ag
+  (package
+    (name "emacs-ag")
+    (version "0.47")
+    (source (origin
+              (method url-fetch)
+              (uri (string-append
+                    "https://github.com/Wilfred/ag.el/archive/"
+                    version ".tar.gz"))
+              (file-name (string-append name "-" version ".tar.gz"))
+              (sha256
+               (base32
+                "1rlmp6wnyhqfg86dbz17r914msp58favn4kd4yrdwyia265a4lar"))))
+    (build-system emacs-build-system)
+    (arguments
+     `(#:phases
+       (modify-phases %standard-phases
+         (add-before 'install 'patch-exec-paths
+           (lambda* (#:key inputs #:allow-other-keys)
+             (emacs-substitute-variables "ag.el"
+               ("ag-executable"
+                (string-append (assoc-ref inputs "the-silver-searcher")
+                               "/bin/ag")))
+             #t)))))
+    (inputs
+     `(("the-silver-searcher" ,the-silver-searcher)))
+    (propagated-inputs
+     `(("dash" ,emacs-dash)
+       ("s" ,emacs-s)))
+    (home-page "https://github.com/Wilfred/ag.el")
+    (synopsis "Front-end for ag (the-silver-searcher) for Emacs")
+    (description "This package provides the ability to use the silver
+searcher, a code searching tool, sometimes abbreviated to @code{ag}.  Features
+include version control system awareness, use of Perl compatible regular
+expressions, editing the search results directly and searching file names
+rather than the contents of files.")
+    (license license:gpl3+)))
+
 (define-public emacs-async
   (package
     (name "emacs-async")