cgit: Render org mode README files.

* guix/forge/cgit.scm: Import emacs-minimal from (gnu packages emacs).
(%cgit-readme): Add README.org.
(about-filter-gexp): Render org mode README files.
* guix/forge/org2html.el: New file.
* doc/forge.skb (Services)[Git web viewers]{cgit service}: Document
support for org mode README files.

3 files changed, 43 insertions, 3 deletions

diff --git a/doc/forge.skb b/doc/forge.skb
index be1260c..077a449 100644
--- a/doc/forge.skb
+++ b/doc/forge.skb
@@ -201,8 +201,8 @@ web. Our cgit service features]
             (item [syntax highlighting for a wide variety of
 programming languages using ,(ref :url "https://pygments.org/" :text
 "Pygments")])
-            (item [rendering markdown, reStructuredText, man page,
-HTML or plain text README files in the ,(emph [About]) page])
+            (item [rendering markdown, org mode, reStructuredText, man
+page, HTML or plain text README files in the ,(emph [About]) page])
             (item [hiding full email addresses on cgit web pages]))
            [Note that this service is different from the cgit service
 of the same name in Guix upstream.])
diff --git a/guix/forge/cgit.scm b/guix/forge/cgit.scm
index 6ac7589..f652825 100644
--- a/guix/forge/cgit.scm
+++ b/guix/forge/cgit.scm
@@ -21,6 +21,7 @@
   #:use-module (forge fcgiwrap)
   #:use-module (forge nginx)
   #:use-module (forge socket)
+  #:use-module ((gnu packages emacs) #:select (emacs-minimal))
   #:use-module ((gnu packages mail) #:select (mailcap))
   #:use-module ((gnu packages version-control)
                 #:select (cgit git-minimal))
@@ -55,7 +56,7 @@
 
 (define %cgit-readme
   (append (list "README.md" "README.markdown" "README.mdown" "README.mkd"
-                "README.rst")
+                "README.org" "README.rst")
           ;; man page READMEs
           (map (lambda (n)
                  (string-append "README." (number->string n)))
@@ -145,6 +146,10 @@ configured in @var{config}."
                    (string-suffix-ci? ".mkd" about-file))
                (invoke #$(file-append cgit "/lib/cgit/filters/html-converters/md2html")
                        about-file))
+              ((string-suffix-ci? ".org" about-file)
+               (invoke #$(file-append emacs-minimal "/bin/emacs")
+                       "--script"
+                       #$(local-file "org2html.el")))
               ((string-suffix-ci? ".rst" about-file)
                (invoke #$(file-append cgit "/lib/cgit/filters/html-converters/rst2html")
                        about-file))
diff --git a/guix/forge/org2html.el b/guix/forge/org2html.el
new file mode 100644
index 0000000..b311331
--- /dev/null
+++ b/guix/forge/org2html.el
@@ -0,0 +1,35 @@
+;;; guix-forge --- Guix software forge meta-service
+;;; Copyright © 2023 Arun Isaac <arunisaac@systemreboot.net>
+;;;
+;;; This file is part of guix-forge.
+;;;
+;;; guix-forge is free software: you can redistribute it and/or modify
+;;; it under the terms of the GNU General Public License as published
+;;; by the Free Software Foundation, either version 3 of the License,
+;;; or (at your option) any later version.
+;;;
+;;; guix-forge is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;;; General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with guix-forge.  If not, see
+;;; <https://www.gnu.org/licenses/>.
+
+(require 'ox-html)
+
+(setq org-export-with-section-numbers nil
+      org-export-with-toc nil)
+
+(defun pipe-stdin-into-current-buffer ()
+  (when-let (line (ignore-errors
+		    (read-from-minibuffer "")))
+    (insert line "\n")
+    (pipe-stdin-into-current-buffer)))
+
+;; TODO: Syntax highlight src code blocks using emacs-htmlize.
+(with-temp-buffer
+  (pipe-stdin-into-current-buffer)
+  (org-html-export-as-html nil nil nil t)
+  (princ (buffer-string)))