From 45e54a085dd8f90cf8e1c3b910b4c07946d0c9cd Mon Sep 17 00:00:00 2001
From: Cayla Hamann <chamann@newrelic.com>
Date: Fri, 10 Jul 2020 11:20:27 -0400
Subject: [PATCH] feat: uses git history to determine date last modified

---
 gatsby-node.js                 | 12 ++++++++++++
 src/templates/GuideTemplate.js | 10 ++++------
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/gatsby-node.js b/gatsby-node.js
index cf7e593c1..c63b83cd5 100644
--- a/gatsby-node.js
+++ b/gatsby-node.js
@@ -1,4 +1,5 @@
 const path = require(`path`);
+const { execSync } = require('child_process');
 
 const getFileRelativePath = (absolutePath) =>
   absolutePath.replace(`${process.cwd()}/`, '');
@@ -59,6 +60,17 @@ exports.createPages = async ({ actions, graphql, reporter }) => {
 
 exports.onCreateNode = ({ node, actions }) => {
   // if we don't have a relative path, attempt to get one
+  if (node.internal.type === 'Mdx' && node.fileAbsolutePath) {
+    const gitAuthorTime = execSync(
+      `git log -1 --pretty=format:%aI ${node.fileAbsolutePath}`
+    ).toString();
+    actions.createNodeField({
+      node,
+      name: 'gitAuthorTime',
+      value: gitAuthorTime,
+    });
+  }
+
   if (node.context && !node.context.fileRelativePath) {
     const { createPage } = actions;
     const { path, component } = node;
diff --git a/src/templates/GuideTemplate.js b/src/templates/GuideTemplate.js
index 75d273bc5..cbcfcba64 100644
--- a/src/templates/GuideTemplate.js
+++ b/src/templates/GuideTemplate.js
@@ -11,7 +11,7 @@ import styles from './GuideTemplate.module.scss';
 
 const GuideTemplate = ({ data }) => {
   const { mdx } = data;
-  const { frontmatter, body, parent } = mdx;
+  const { frontmatter, body, fields } = mdx;
   const { title, description, duration } = frontmatter;
 
   return (
@@ -28,7 +28,7 @@ const GuideTemplate = ({ data }) => {
       </div>
       <MDXContainer>{body}</MDXContainer>
       <div className={styles.lastUpdated}>
-        {`Page last modified on ${parent.modifiedTime}`}
+        {`Page last modified on ${fields.gitAuthorTime}`}
       </div>
     </Layout>
   );
@@ -48,10 +48,8 @@ export const pageQuery = graphql`
         title
         description
       }
-      parent {
-        ... on File {
-          modifiedTime(formatString: "MMMM DD, YYYY")
-        }
+      fields {
+        gitAuthorTime(formatString: "MMMM DD, YYYY")
       }
     }
   }