Detects the commit range of a PR on CircleCI since the last successful status check

detectCommitRange.sh

# Build what's changed in the HEAD commit by default
COMMIT_RANGE="$CIRCLE_SHA1"

# If this is a PR, diff the changes over time against ther commit status
# according to the Github API.
# TODO: This should move to a Circle Orb cause OSS is sweet.
if ! [[ -z ${CIRCLE_PULL_REQUEST+x} ]];
then
  GITHUB_USER=wellth-app
  GITHUB_REPO_NAME=react-components
  GITHUB_API_URI=https://api.github.com
  GITHUB_REPO_PATH=$GITHUB_API_URI/repos/$GITHUB_USER/$GITHUB_REPO_NAME
  GITHUB_AUTHORIZATION_HEADER="Authorization: token $GITHUB_API_TOKEN"
  GITHUB_PR_NUMBER=${CIRCLE_PULL_REQUEST##*/}

  # Hit the github API for PR commit range
  # !!!: Accept header is to include draft pull requests.
  GITHUB_PULL_REQUEST=$(curl -H "$GITHUB_AUTHORIZATION_HEADER" \
  -H "Accept: application/vnd.github.shadow-cat-preview+json" \
  $GITHUB_REPO_PATH/pulls/$GITHUB_PR_NUMBER)

  BASE=$(echo $GITHUB_PULL_REQUEST | jq '.base.sha' | tr -d '"')
  HEAD=$(echo $GITHUB_PULL_REQUEST | jq '.head.sha' | tr -d '"')

  # Get the commits from BASE...HEAD, exclusive.
  # `rev-list` exludes base from it's return value
  # while adding `^` ensures we compare up to the commit
  # before HEAD.
  for commit in $(git rev-list $BASE...$HEAD^)
  do
    # Get the commit status from github
    COMMIT_STATUS=$(curl -H "$GITHUB_AUTHORIZATION_HEADER" \
      $GITHUB_REPO_PATH/commits/$commit/status | jq '.state')

    if [ $COMMIT_STATUS == 'success' ];
    then
      BASE=$commit
      continue
    fi
  done

  COMMIT_RANGE="$BASE...$HEAD"
fi

echo "Building over commit range: $COMMIT_RANGE"