fix: use bundler to manage ruby environment (#15)

use bundler to create an isolated environment and install dependencies
into it

then use it to execute bashly within that environment

lib/bashly_wrapper.sh

@@ -4,6 +4,9 @@ set -Eeuo pipefail
 current_script_path=${BASH_SOURCE[0]}
 bin_dir="$(dirname "${current_script_path}")"
 install_dir="$(dirname "${bin_dir}")"
-gem_home="${install_dir}/gem_home"
+gem_home="${install_dir}/gem"
 
-GEM_HOME="${gem_home}" "${gem_home}/bin/bashly" "${@}"
+PATH="${gem_home}/bin:${PATH}" \
+	BUNDLE_GEMFILE="${install_dir}/Gemfile" \
+	BUNDLE_PATH="${install_dir}/artifacts" \
+	bundle exec bashly "${@}"

lib/utils.bash

@@ -32,15 +32,47 @@ list_all_versions() {
 	list_github_tags
 }
 
+ensure_bundler() {
+	if command -v bundle &>/dev/null && bundle --version &>/dev/null; then
+		return 0
+	fi
+
+	gem install --no-user-install bundler
+}
+
+create_bundle() {
+	local working_dir="${1}"
+	pushd "${working_dir}" &>/dev/null
+
+	ensure_bundler
+	bundle init
+	mkdir -p artifacts
+	bundle config set path artifacts
+	bundle add bashly --version "= ${version}"
+
+	# get rid of warnings at runtime
+	#
+	# these deps are in the ruby stdlib, but will soon
+	# be moved to their own gems. installing them gets
+	# rid of that warning.
+	bundle add fiddle
+	bundle add logger
+
+	popd &>/dev/null
+}
+
 download_release() {
 	local version download_dir
 	version="$1"
 	download_dir="$2"
 
-	local gem_home="${download_dir}/gem_home"
+	local gem_home="${download_dir}/gem"
 	mkdir -p "${gem_home}"
 
-	GEM_HOME="${gem_home}" gem install "${TOOL_NAME}:${version}"
+	GEM_HOME="${gem_home}" \
+		GEM_PATH="${gem_home}" \
+		PATH="${gem_home}/bin:${PATH}" \
+		create_bundle "${download_dir}"
 }
 
 install_version() {