message: reuse builds from ECR more efficiently
diff: @@ -4,8 +4,8 @@ const glob = require('glob');
  const { join, resolve } = require('path');
  const { emptyDirSync, copySync } = require('fs-extra');
  const { execSync } = require('child_process');
  -
  const root = resolve(join(__dirname, '..'));
  +const specialBranches = [ 'master' ];
  const context = join(root, 'deploy/context');
  const depLayerFiles = [ 'package.json' ];
  const codeLayerFiles = [
  @@ -38,7 +38,8 @@ codeLayerFiles.forEach(serverFile => {
  });
  });
  -let dockerImageLabel = process.env.TRAVIS_BUILD_ID;
  +let dockerImageLabel = specialBranches.includes(process.env.TRAVIS_BRANCH) ? process.env.TRAVIS_BRANCH : process.env.TRAVIS_BUILD_ID || 'latest';
  +
  try {
  process.stdout.write(`Retrieving docker build from ${process.env.ECR_ENDPOINT}:${dockerImageLabel} ...`);
  execSync(`docker pull ${process.env.ECR_ENDPOINT}:${dockerImageLabel}`);
  