old_contents: const { promisify } = require('util');
  const fs = require('fs');
  const readFile = promisify(fs.readFile);
  const writeFile = promisify(fs.writeFile);
  const readdir = promisify(fs.readdir);
  const Talks = require('./src/site/_data/talks');
  
  const main = async () => {
    const files = await readdir(__dirname + '/redirects');
    const contents = await Promise.all(
      files.map(filename => {
        return readFile(__dirname + '/redirects/' + filename, 'utf8').then(
          url => {
            return `/${filename.trim()} ${url.trim()} 307`;
          }
        );
      })
    );
  
    const talks = await Talks();
  
    const years = new Set();
  
    // add the api
    contents.push(
      '/api /api/index.json 200',
      ...talks.map(_ => {
        years.add(_.event.year);
        return `/api/session/${_.slug} /api/session/${_.slug}/index.json 200`;
      }),
      ...Array.from(years).map(
        year => `/api/event/${year} /api/event/${year}/index.json 200`
      )
    );
  
    await writeFile(__dirname + '/dist/_redirects', contents.join('\n'));
  };
  
  main();
  
new_contents: const { promisify } = require('util');
  const fs = require('fs');
  const readFile = promisify(fs.readFile);
  const writeFile = promisify(fs.writeFile);
  const readdir = promisify(fs.readdir);
  const Talks = require('./src/site/_data/talks');
  
  const main = async () => {
    const files = await readdir(__dirname + '/redirects');
    const contents = await Promise.all(
      files.map(filename => {
        return readFile(__dirname + '/redirects/' + filename, 'utf8').then(
          url => {
            return `/${filename.trim()} ${url.trim()} 307`;
          }
        );
      })
    );
  
    const talks = await Talks();
  
    const years = new Set();
  
    // add the api
    contents.push(
      '/api /api/index.json 200',
      ...talks.map(_ => {
        years.add(_.event.year);
        return `/api/session/${_.slug} /api/session/${_.slug}/index.json 200`;
      }),
      ...Array.from(years).map(
        year => `/api/event/${year} /api/event/${year}/index.json 200`
      ),
      '/api/* /api/404.json 404'
    );
  
    await writeFile(__dirname + '/dist/_redirects', contents.join('\n'));
  };
  
  main();
  
subject: add 404 for api