gnu: Add emacs-font-lock-studio.

* gnu/packages/emacs-xyz.scm (emacs-font-lock-studio): New variable.

gnu/packages/emacs-xyz.scm

@@ -3196,6 +3196,33 @@ environment set through Direnv.")
 that the binary uses instead of the actual binary contents.")
     (license license:gpl3+)))
 
+(define-public emacs-font-lock-studio
+  (package
+    (name "emacs-font-lock-studio")
+    (version "20170127.2051")           ;melpa version
+    (source
+     (origin
+       (method git-fetch)
+       (uri (git-reference
+             (url "https://github.com/Lindydancer/font-lock-studio")
+             (commit "12c35967b31233e06946c70627aa3152dacfe261")))
+       (file-name (git-file-name name version))
+       (sha256
+        (base32 "0q0s6f5vi3sfifj7vq2nnsmgyyivp1sd3idk32858md5ri71qif0"))))
+    (build-system emacs-build-system)
+    (home-page "https://github.com/Lindydancer/font-lock-studio")
+    (synopsis "Interactive debugger for Font Lock keywords")
+    (description
+     "Font Lock Studio is an interactive debugger for Emacs syntax highlighting
+rules, also called Font Lock keywords.  It can @emph{single-step} Font Lock
+keywords -- matchers, highlights, and anchored rules, to see what happens when
+a buffer is fontified.  Breakpoints can be set on or inside rules.  When
+inside a rule, matches are visualized using a palette of background colors.
+The explainer can describe a rule in plain-text English.  Finally, tight
+integration with Edebug allows stepping into Lisp expressions that are part of
+the Font Lock keywords.")
+    (license license:gpl3+)))
+
 (define-public emacs-form-feed
   (package
     (name "emacs-form-feed")