gnu: Add emacs-helm-gtags.

* gnu/packages/emacs.scm (emacs-helm-gtags): New public variable.

gnu/packages/emacs.scm

@@ -8277,3 +8277,23 @@ arXiv, Google Scholar, Library of Congress, etc.
       (description "@code{ewmctrl} provides an Emacs interface to
 @code{wmctrl} command-line window-management program.")
       (license license:gpl3+))))
+
+(define-public emacs-helm-gtags
+  (package
+    (name "emacs-helm-gtags")
+    (version "1.5.6")
+    (source (origin
+              (method url-fetch)
+              (uri (string-append
+                    "https://github.com/syohex/emacs-helm-gtags/archive/"
+                    version ".tar.gz"))
+              (file-name (string-append name "-" version ".tar.gz"))
+              (sha256
+               (base32
+                "1a10snhg6nnnan6w9a7mcziy26vxbsr3c35i0gcarnkdp2yqng36"))))
+    (build-system emacs-build-system)
+    (home-page "https://github.com/syohex/emacs-helm-gtags")
+    (synopsis "Emacs Helm interface to GNU Global")
+    (description
+     "@code{emacs-helm-gtags} provides a Emacs Helm interface to GNU Global.")
+    (license license:gpl3+)))