promote_slug.sh

#!/usr/bin/env bash

set -eu

# Finds the heroku slug id from the compile apps latests releases
# via the commit SHA
function heroku_slug () {
  heroku releases --app ${1} --json | \
    jq -rc --arg commit "${2}" \
            '.[]
            | select(.description | test("Deploy .*"))
            | (.description | gsub("Deploy "; "")) as $commit_hash
            | select($commit_hash | test($commit))
            | .slug.id'
}

# Copies a slug to an application
function promote_slug () {
  local app=${1}
  local slug=${2}
  local commit=${3}
  heroku api POST "/apps/${app}/releases" --body '{"slug": "'"${slug}"'", "description": "Deploy '"${commit}"'"}' | tee release.json
  local version=$(jq '.version' release.json)
  sleep 5
  heroku releases:output ${version} -a ${app}
  sleep 5
  heroku releases:info ${version} --app $app --json
  heroku releases:info ${version} --app $app --json | grep status | grep -q succeeded
}

FIVE_MINUTES=$((60 * 5))
COMPILE_APP=${1}
APP=${2}
CURRENT_COMMIT=${CIRCLE_SHA1}
HEAD_COMMIT=$(git rev-parse origin/master)
COMMIT_BEFORE_HEAD=$(git rev-parse origin/master~1)
CURRENT_TIME=$(date +%s)
COMMIT_TIME=$(git show --format='%ct' origin/master | head -n1)
SECONDS_SINCE_COMMIT=$(expr $CURRENT_TIME - $COMMIT_TIME)
CURRENT_COMMIT_SHORT=${CURRENT_COMMIT:0:8}

echo "-----> Trying to find precompile slug for ${CURRENT_COMMIT} on ${COMPILE_APP}"
SLUG=$(heroku_slug ${COMPILE_APP} ${CURRENT_COMMIT_SHORT})

# If we found a slug id try and promote it to production, fallback to
# old-school deploys if we can't find one
if [ ! -z "${SLUG}" ] ; then
  echo "-----> Trying to promote ${SLUG} to ${APP}..."
  if [ "${HEAD_COMMIT}" == "${CURRENT_COMMIT}" ] ;  then
    echo "       origin/master is at ${CURRENT_COMMIT}."
    echo "       Promoting slug..."
    promote_slug ${APP} ${SLUG} ${CURRENT_COMMIT_SHORT}
  elif [ "${COMMIT_BEFORE_HEAD}" == "${CURRENT_COMMIT}" ] && [ "${SECONDS_SINCE_COMMIT}" -lt "$FIVE_MINUTES" ] ; then
    echo "       Next commit on master (${HEAD_COMMIT}) merged less than 5 minutes ago - safe to deploy."
    echo "       Promoting slug..."
    promote_slug ${APP} ${SLUG} ${CURRENT_COMMIT_SHORT}
  else
    echo "       Either the next commit on master (${HEAD_COMMIT}) merged more than 5 minutes ago"
    echo "       or there are multiple commits on master ahead."
    echo "       This commit will deploy with the next run."
  fi
else
  echo "-----> Couldn't find precompiled slug - falling back"
  echo "       Could not find a precompiled slug on ${APP}"
  echo "       Looked for ${CURRENT_COMMIT}"
  echo "       Falling back to regular deploys..."
  deploy ${APP}
fi