Re-add GitHub Metadata plugin, add another default SHA env

Gemfile

@@ -14,7 +14,8 @@ group :jekyll_plugins do
   gem "jekyll-feed", "~> 0.12"
   gem "jekyll-last-modified-at"
   gem "jekyll-redirect-from"
-  gem 'jekyll-environment-variables'
+  gem "jekyll-environment-variables"
+  gem "jekyll-github-metadata"
   gem "jekyll-sitemap"
 end
 

Gemfile.lock

@@ -10,6 +10,10 @@ GEM
       http_parser.rb (~> 0)
     eventmachine (1.2.7)
     eventmachine (1.2.7-x64-mingw32)
+    faraday (2.5.2)
+      faraday-net_http (>= 2.0, < 3.1)
+      ruby2_keywords (>= 0.0.4)
+    faraday-net_http (3.0.0)
     ffi (1.15.5)
     ffi (1.15.5-x64-mingw32)
     forwardable-extended (2.6.0)
@@ -35,6 +39,9 @@ GEM
       jekyll (>= 3.0, < 5.x)
     jekyll-feed (0.15.1)
       jekyll (>= 3.7, < 5.0)
+    jekyll-github-metadata (2.15.0)
+      jekyll (>= 3.4, < 5.0)
+      octokit (~> 4.0, != 4.4.0)
     jekyll-last-modified-at (1.3.0)
       jekyll (>= 3.7, < 5.0)
       posix-spawn (~> 0.3.9)
@@ -55,6 +62,9 @@ GEM
       rb-fsevent (~> 0.10, >= 0.10.3)
       rb-inotify (~> 0.9, >= 0.9.10)
     mercenary (0.4.0)
+    octokit (4.25.1)
+      faraday (>= 1, < 3)
+      sawyer (~> 0.9)
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
     posix-spawn (0.3.15)
@@ -64,11 +74,15 @@ GEM
       ffi (~> 1.0)
     rexml (3.2.5)
     rouge (3.28.0)
+    ruby2_keywords (0.0.5)
     safe_yaml (1.0.5)
     sassc (2.4.0)
       ffi (~> 1.9)
     sassc (2.4.0-x64-mingw32)
       ffi (~> 1.9)
+    sawyer (0.9.2)
+      addressable (>= 2.3.5)
+      faraday (>= 0.17.3, < 3)
     terminal-table (1.8.0)
       unicode-display_width (~> 1.1, >= 1.1.1)
     thread_safe (0.3.6)
@@ -88,6 +102,7 @@ DEPENDENCIES
   jekyll (~> 4.1.1)
   jekyll-environment-variables
   jekyll-feed (~> 0.12)
+  jekyll-github-metadata
   jekyll-last-modified-at
   jekyll-redirect-from
   jekyll-sitemap

_layouts/base.html

@@ -8,7 +8,7 @@ layout: compress
         <meta content="width=device-width" name="viewport">
         <link as="style" href="/assets/main.css" rel="preload">
         <link href="/assets/main.css" rel="stylesheet">
-        <!-- build-commit-id: {{ site.github.build_revision }} -->
+        <!-- build-commit-id: {{ site.github.build_revision | default: site.env.GITHUB_SHA }} -->
         <!--    <link rel="stylesheet" href="/assets/print.css" media="print">-->
         <link href="/assets/rouge.css" rel="stylesheet">
         <title>