Allow the Pull Request to trigger a build.

_scripts/travis/cibuild.sh

@@ -0,0 +1,28 @@
+#!/bin/bash
+
+# Travis CI build jobs.
+#
+# © 2019 Cotes Chung
+# Published under MIT License
+
+if [[ $TRAVIS_PULL_REQUEST = "false" ]]; then # triggered by author
+
+  BUILDER=../blog-builder
+
+  git clone https://${GH_TOKEN}@github.com/cotes2020/blog-builder.git \
+    $BUILDER --depth=1 -q
+
+  cp -r $BUILDER/framework/* .
+  bash _cibuild.sh
+
+else # triggered by Pull Request
+
+  bundle install --path vendor/bundle --quiet
+  python _scripts/py/init_all.py
+
+  build_cmd="JEKYLL_ENV=production bundle exec jekyll build"
+
+  echo "\$ $build_cmd"
+  eval $build_cmd
+
+fi