gnu: Add emacs-helm-ag.

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

Signed-off-by: Oleg Pykhalov <go.wigust@gmail.com>

gnu/packages/emacs-xyz.scm

@@ -6292,6 +6292,31 @@ not tied in the trap of backward compatibility.")
 for search-based navigation of buffers.")
     (license license:gpl2+)))
 
+(define-public emacs-helm-ag
+  (let ((commit "2fc02c4ead29bf0db06fd70740cc7c364cb650ac")
+        (revision "1"))
+    (package
+      (name "emacs-helm-ag")
+      (version "0.58")
+      (source
+       (origin
+         (method git-fetch)
+         (uri (git-reference
+               (url "https://github.com/syohex/emacs-helm-ag.git")
+               (commit commit)))
+         (file-name (git-file-name name version))
+         (sha256
+          (base32 "1gnn0byywbld6afcq1vp92cjvy4wlag9d1wgymnqn86c3b1bcf21"))))
+      (build-system emacs-build-system)
+      (propagated-inputs
+       `(("emacs-helm" ,emacs-helm)))
+      (home-page "https://github.com/syohex/emacs-helm-ag")
+      (synopsis "Helm interface to the Silver Searcher")
+      (description
+       "This package provides a frontend for grepping tools like ag and ack,
+as well as features for editing search results.")
+      (license license:gpl3+))))
+
 (define-public emacs-helm-projectile
   (package
     (name "emacs-helm-projectile")