gnu: Add emacs-highlight-stages.

* gnu/packages/emacs.scm (emacs-highlight-stages): New variable.
* gnu/packages/patches/emacs-highlight-stages-add-gexp.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add this.

gnu/local.mk

@@ -608,6 +608,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/einstein-build.patch			\
   %D%/packages/patches/emacs-exec-path.patch			\
   %D%/packages/patches/emacs-fix-scheme-indent-function.patch	\
+  %D%/packages/patches/emacs-highlight-stages-add-gexp.patch	\
   %D%/packages/patches/emacs-scheme-complete-scheme-r5rs-info.patch	\
   %D%/packages/patches/emacs-source-date-epoch.patch		\
   %D%/packages/patches/erlang-man-path.patch			\

gnu/packages/emacs.scm

@@ -4861,6 +4861,31 @@ (define-public emacs-highlight-sexp
      "This Emacs package highlights the s-exp at the current position.")
     (license license:gpl3+)))
 
+(define-public emacs-highlight-stages
+  (let ((commit "29cbc5b78261916da042ddb107420083da49b271")
+        (revision "1"))
+    (package
+      (name "emacs-highlight-stages")
+      (version (string-append "1.1.0" "-" revision "." (string-take commit 7)))
+      (source
+       (origin
+         (method git-fetch)
+         (uri (git-reference
+               (url "https://github.com/zk-phi/highlight-stages.git")
+               (commit commit)))
+         (file-name (string-append name "-" version "-checkout"))
+         (sha256
+          (base32
+           "0r6nbcrr0dqpgm8dir8ahzjy7rw4nrac48byamzrq96r7ajlxlv0"))
+         (patches
+          (search-patches "emacs-highlight-stages-add-gexp.patch"))))
+      (build-system emacs-build-system)
+      (home-page "https://github.com/wigust/highlight-stages")
+      (synopsis "Minor mode that highlights (quasi-quoted) expressions")
+      (description "@code{highlight-stages} provides an Emacs minor mode that
+highlights quasi-quoted expressions.")
+      (license license:gpl3+))))
+
 (define-public emacspeak
   (package
     (name "emacspeak")

gnu/packages/patches/emacs-highlight-stages-add-gexp.patch

@@ -0,0 +1,26 @@
+Copyright © 2017 Oleg Pykhalov <go.wigust@gmail.com>
+Copyright © 2017 Ludovic Courtès <ludo@gnu.org>
+
+This patch adds highlighting for (guix) G-Expressions.
+
+diff --git a/highlight-stages.el b/highlight-stages.el
+index 3094c3c..e11260e 100644
+--- a/highlight-stages.el
++++ b/highlight-stages.el
+@@ -237,14 +237,14 @@ non-nil, (match-string 0) must be the expression matched."
+ 
+ (defun highlight-stages-lisp-quote-matcher (&optional limit)
+   (when (highlight-stages--search-forward-regexp
+-         "\\(?:`\\|\\(#?'\\)\\)\\|([\s\t\n]*\\(?:backquote\\|\\(quote\\)\\)[\s\t\n]+" limit)
++         "\\(?:`\\|\\(#?'\\)\\)\\|([\s\t\n]*\\(?:backquote\\|\\(quote\\)\\)[\s\t\n]+\\|\\(?:#~\\)\\|([\s\t\n]*\\(?:gexp\\)[\s\t\n]+" limit)
+     (prog1 (if (or (match-beginning 1) (match-beginning 2)) 'real t)
+       (set-match-data
+        (list (point)
+              (progn (ignore-errors (forward-sexp 1)) (point)))))))
+ 
+ (defun highlight-stages-lisp-escape-matcher (&optional limit)
+-  (when (highlight-stages--search-forward-regexp ",@?\\|([\s\t\n]*\\\\,@?+[\s\t\n]+" limit)
++  (when (highlight-stages--search-forward-regexp ",@?\\|([\s\t\n]*\\\\,@?+[\s\t\n]+\\|\\(unquote\\)\\|\\(unquote-splicing\\)\\|\\(ungexp-native\\)\\|\\(ungexp-splicing\\)\\|\\(ungexp-native-splicing\\)\\|\\(ungexp\\)\\|#\\$" limit)
+     (set-match-data
+      (list (point)
+            (progn (ignore-errors (forward-sexp 1)) (point))))