Install Bundler version from Gemfile.lock + add_ruby_env_info (#32)

Author: mokagio

bin/dump_ruby_env_info

@@ -0,0 +1,23 @@
+#!/bin/bash -eu
+
+echo "--- :ruby: Ruby environment info dump ${1:-}"
+
+if [[ -f .ruby-version ]]; then
+  cat .ruby-version
+else
+  echo 'Could not find .ruby-version in current folder'
+fi
+
+set -x # debug mode: print the commands we call
+
+which ruby
+ruby --version
+
+which gem
+gem --version
+
+which bundle
+gem list bundler
+bundle version
+
+set +x # exit debug mode

bin/install_gems

@@ -7,10 +7,13 @@ CACHEKEY="$BUILDKITE_PIPELINE_SLUG-$ARCHITECTURE-ruby$RUBY_VERSION-$GEMFILE_HASH
 
 restore_cache "$CACHEKEY"
 
-# Ensure we're using the latest version of Bundler before running bundle install.
-#
-# See https://github.com/Automattic/bash-cache-buildkite-plugin/issues/16  for more details on why this is recommended.
-gem install bundler
+# Install the same Bundler version as the one in the Gemfile.lock.
+# This should prevent runtime issues where Ruby "gets confused" on which Bundler version to use.
+# See https://github.com/Automattic/bash-cache-buildkite-plugin/issues/16 for more details.
+GEMFILE_LOCK_BUNDLER_VERSION=$(sed -n -e '/BUNDLED WITH/{n;s/ *//p;}' Gemfile.lock)
+# The command will fail if the `--version` parameter is empty; we can omit checking for that ourselves.
+gem install bundler --version "$GEMFILE_LOCK_BUNDLER_VERSION"
+
 bundle install
 
 # If this is the first time we've seen this particular cache key, save it for the future