bash script refactorings

- format with shfmt
- safer curl args
- Use `jq -r` to remove quotes
- consistent use of curlies around variable names

.circleci/eslint-changed-files.sh

@@ -1,25 +1,39 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
-set -eou pipefail
+# Please Use Google Shell Style: https://google.github.io/styleguide/shell.xml
 
-CIRCLE_PR_NUMBER="${CIRCLE_PR_NUMBER:-${CIRCLE_PULL_REQUEST##*/}}" # Determine PR number from pull request link
-  if [[ -v CIRCLE_PR_NUMBER ]] && [ -n ${CIRCLE_PR_NUMBER} ]; then
-    url="https://api.github.com/repos/${DOCKER_REPOSITORY}/pulls/$CIRCLE_PR_NUMBER" # Get PR from github API
-    TARGET_BRANCH=$(curl "$url" | jq '.base.ref' | tr -d '"') # Determine target/base branch from API response
-  fi
+# ---- Start unofficial bash strict mode boilerplate
+# http://redsymbol.net/articles/unofficial-bash-strict-mode/
+set -o errexit  # always exit on error
+set -o errtrace # trap errors in functions as well
+set -o pipefail # don't ignore exit codes when piping output
+set -o posix    # more strict failures in subshells
+# set -x          # enable debugging
 
-  if [ -z "${TARGET_BRANCH}" ] || [  ${TARGET_BRANCH} == "null" ]; then
-    echo "Not a PR. Skipping eslint-changed-files."
-    exit 0
-  fi
+IFS=$'\n\t'
+# ---- End unofficial bash strict mode boilerplate
 
-  echo "Getting list of changed files..."
-  CHANGED_FILES=$(git diff --name-only "origin/${TARGET_BRANCH}"..$CIRCLE_BRANCH -- '*.js' | tr '\n' ' ')
+# Determine PR number from pull request link
+CIRCLE_PR_NUMBER="${CIRCLE_PR_NUMBER:-${CIRCLE_PULL_REQUEST##*/}}"
+if [[ -n "${CIRCLE_PR_NUMBER}" ]]; then
+  # Get PR from github API
+  url="https://api.github.com/repos/${DOCKER_REPOSITORY}/pulls/${CIRCLE_PR_NUMBER}"
+  # Determine target/base branch from API response
+  TARGET_BRANCH=$(curl --silent --location --fail --show-error "${url}" | jq -r '.base.ref')
+fi
 
-  # If we have changed files
-  if [ -n "${CHANGED_FILES}" ]; then
-    echo "Files have been changed. Run eslint against these files."
-    npm run lint:warnings $CHANGED_FILES
-  else
-    echo "We have no changed files, don't run eslint-changed-files"
-  fi
+if [[ -z "${TARGET_BRANCH}" ]] || [[ ${TARGET_BRANCH} == "null" ]]; then
+  echo "Not a PR. Skipping eslint-changed-files."
+  exit 0
+fi
+
+echo "Getting list of changed files..."
+CHANGED_FILES=$(git diff --name-only "origin/${TARGET_BRANCH}"..$CIRCLE_BRANCH -- '*.js')
+
+# If we have changed files
+if [[ -n "${CHANGED_FILES}" ]]; then
+  echo "Files have been changed. Run eslint against these files."
+  echo "${CHANGED_FILES}" | xargs npm run lint:warnings
+else
+  echo "We have no changed files, don't run eslint-changed-files"
+fi