gnu: Add emacs-polymode.

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

gnu/packages/emacs.scm

@@ -6850,6 +6850,32 @@ contexts.
 @end itemize\n")
     (license license:gpl3+)))
 
+(define-public emacs-polymode
+  ;; There hasn't been a proper release.
+  (let ((commit "0340f5e7e55235832e59673f027cc79a23cbdcd6")
+        (revision "1"))
+    (package
+      (name "emacs-polymode")
+      (version (string-append "1.0-" revision "." (string-take commit 7)))
+      (source (origin
+                (method git-fetch)
+                (uri (git-reference
+                      (url "https://github.com/vspinu/polymode.git")
+                      (commit commit)))
+                (file-name (string-append name "-" version "-checkout"))
+                (sha256
+                 (base32
+                  "057cybkq3cy07n5s332k071sjiky3mziy003lza4rh75mgqkwhmh"))))
+      (build-system emacs-build-system)
+      (home-page "https://github.com/vspinu/polymode")
+      (synopsis "Framework for multiple Emacs modes based on indirect buffers")
+      (description "Polymode is an Emacs package that offers generic support
+for multiple major modes inside a single Emacs buffer.  It is lightweight,
+object oriented and highly extensible.  Creating a new polymode typically
+takes only a few lines of code.  Polymode also provides extensible facilities
+for external literate programming tools for exporting, weaving and tangling.")
+      (license license:gpl3+))))
+
 (define-public eless
   (package
     (name "eless")