Travis: add automated release steps

Author: codenirvana

.travis.yml

@@ -18,6 +18,55 @@ jobs:
         - npm run test-unit
         - bash <(curl -s https://codecov.io/bash) -c -Z -f .coverage/coverage-final.json -F unit
 
+    # create a new release if $CREATE_RELEASE is set
+    - stage: Create Release
+      if: env(CREATE_RELEASE) = true AND type = api AND tag IS blank
+      os: osx
+      node_js: 12
+      git:
+        depth: false # disable --depth
+      script:
+        # fail-fast using set -e
+        - set -e
+        # decrypt and ssh-add the deploy-key
+        - openssl aes-256-cbc -K $encrypted_05f822b6caa8_key -iv $encrypted_05f822b6caa8_iv
+          -in .github/travis-deploy-key.enc -out /tmp/travis-deploy-key -d
+        - chmod 600 /tmp/travis-deploy-key
+        - eval "$(ssh-agent -s)"
+        - ssh-add /tmp/travis-deploy-key
+        - rm /tmp/travis-deploy-key
+        # convert remote URL from HTTPS to SSH
+        - git remote set-url origin $(git config --get remote.origin.url | sed -E 's#(http.*://)([^/]+)/(.+)$#git@\2:\3#g')
+        - ssh-keyscan github.com >> ~/.ssh/known_hosts
+        # create release
+        - npm run release $PUSH_TO_ORIGIN $PRERELEASE_SUFFIX
+        - set +e
+
+    # publish npm package on tagged builds
+    - stage: Publish Package
+      if: tag IS present
+      os: osx
+      node_js: 12
+      git:
+        depth: false # disable --depth
+      script:
+        # fail-fast using set -e
+        - set -e
+        # get prerelease suffix from version tag
+        - TAG=$(echo $TRAVIS_TAG | sed 's/^.*-\([a-z]*\).*$/\1/')
+        # set to `latest` in case of no suffix
+        - TAG=$([ "${TAG}" = "$TRAVIS_TAG" ] && echo "latest" || echo $TAG)
+        # make sure `latest` tag is create from master branch
+        - '[ "$TAG" = "latest" ] && [ $(git rev-parse HEAD) != $(git rev-parse origin/master) ] && return 1 || return 0'
+        - set +e
+      deploy:
+        edge: true # opt in to dpl v2
+        provider: npm
+        tag: $TAG
+        on:
+          tags: true
+          all_branches: true
+
     # update gh-pages docs on master
     - stage: Publish Docs
       if: branch = master