gatsby-node.js

const path = require(`path`)
const fetch = require('node-fetch');
const fs = require('file-system');

// Add URLs to v2 indexes to this array for them to be rendered on the website
// If the index does not need to be downloaded, place the index.yaml in src/data/indexes
// Note: this is only for developement add URLs to /ci/get-indexes.sh to affect production
const indexURLs = [
  'https://github.com/appsody/stacks/releases/latest/download/stable-index.yaml',
  'https://github.com/appsody/stacks/releases/latest/download/incubator-index.yaml',
  'https://github.com/appsody/stacks/releases/latest/download/experimental-index.yaml'
]

const { createFilePath } = require(`gatsby-source-filesystem`)

exports.onCreateNode = ({ node, getNode, actions }) => {
  const { createNodeField } = actions
  if (node.internal.type === `MarkdownRemark`) {
    const slug = createFilePath({ node, getNode })
   
    if (slug == '/overview/') {
      createNodeField({
        node,
        name: `slug`,
        value: `/docs`,
      })
    } else {
      createNodeField({
        node,
        name: `slug`,
        value: `/docs${slug}`,
      })
    }
  }
}

exports.onPreInit = () => {
  indexURLs.forEach(url => {
    fetch(url)
    .then(res => res.text())
    .then(body => {
        const fileName = url.split('/').reverse()[0];
        fs.writeFile(`src/data/indexes/${fileName}`, body);
      })
  })
}

exports.createPages = ({ actions, graphql }) => {
  const { createPage, createRedirect } = actions

  const docTemplate = path.resolve(`src/templates/docTemplate.js`)

  return graphql(`
    {
      allMarkdownRemark {
        edges {
          node {
            fields {
              slug
            }
          }
        }
      }
    }
  `).then(result => {
    if (result.errors) {
      return Promise.reject(result.errors)
    }

    return result.data.allMarkdownRemark.edges.forEach(({ node }) => {
      if (node.fields.slug == '/docs/overview/') {
        node.fields.slug = '/docs'
      }
      createPage({
        path: node.fields.slug,
        component: docTemplate,
        context: {
        },
      })
    })
  })
}