Include build date / git rev somewhere we can scrape

Change-Id: Ie15b96f633883f443f80e7335a1365a1a5687d1d

_plugins/jekyll-version.rb

@@ -0,0 +1,12 @@
+module Jekyll
+  class VersionGenerator < Generator
+    priority :high
+    safe true
+
+    def generate(site)
+      site.data["version"] = {}
+      site.data["version"]["git"] = %x( git describe --always --dirty).strip
+      site.data["version"]["build_date"] = %x( date +%s ).strip
+    end
+  end
+end

version.json

@@ -0,0 +1,9 @@
+---
+title: version
+layout: none
+search: exclude
+---
+{
+    "git": "{{site.data.version.git}}",
+    "build_date": "{{site.data.version.build_date}}"
+}