message: Clarifying documentation
diff: @@ -45,6 +45,9 @@ WORKSPACE="${WORKSPACE:-$(upsearch WORKSPACE)}"
  ROOT_CONTAINER=${ROOT_CONTAINER:-tensorflow/tensorflow}
  TF_ROOT_CONTAINER_TAG=${ROOT_CONTAINER_TAG:-devel}
  +
  +# TF_BUILD_VERSION can be either a tag, branch, commit ID or PR number.
  +# For a PR, set TF_BUILD_VERSION_IS_PR="yes"
  TF_BUILD_VERSION=${TF_DOCKER_BUILD_DEVEL_BRANCH:-master}
  TF_BUILD_VERSION_IS_PR=${TF_DOCKER_BUILD_DEVEL_BRANCH_IS_PR:-no}
  TF_REPO=${TF_REPO:-https://github.com/tensorflow/tensorflow}
  @@ -164,7 +167,7 @@ function test_container()
  function checkout_tensorflow()
  {
  if [[ "$#" != "3" ]]; then
  - die "Usage: ${FUNCNAME} <REPO_URL> <BRANCH/TAG/COMMIT-ID> <TF_BUILD_VERSION_IS_PR>"
  + die "Usage: ${FUNCNAME} <REPO_URL> <BRANCH/TAG/COMMIT-ID/PR-ID> <TF_BUILD_VERSION_IS_PR>"
  fi
  TF_REPO="${1}"
  @@ -177,10 +180,10 @@ function checkout_tensorflow()
  # Clean any existing tensorflow sources
  rm -rf "${TENSORFLOW_DIR}"
  - # Let's make this simeple for now; we can be more fancy later
  git clone ${TF_REPO} ${TENSORFLOW_DIR}
  cd ${TENSORFLOW_DIR}
  if [[ "${TF_BUILD_VERSION_IS_PR}" == "yes" ]]; then
  + # If TF_BUILD_VERSION is a PR number, then fetch first
  git fetch origin pull/${TF_BUILD_VERSION}/head:pr-${TF_BUILD_VERSION}
  git checkout pr-${TF_BUILD_VERSION}
  else
  