edit_requirements_txt_for_downstream_in_subdir: check for changes

  # "warning: filtering not recognized by server, ignoring"

  (cd ..; git fetch --unshallow)

  local PRJ_NAME

  local REQ_TXT_TO_EDIT

  local TMP_FOR_COMPARISON="zzztmp-ci-support-req.txt"

  PRJ_NAME="$(basename "$GITHUB_REPOSITORY")"

  sed -i "/egg=$PRJ_NAME/ c git+file://$(readlink -f ..)#egg=$PRJ_NAME" requirements.txt

  REQ_TXT_TO_EDIT="$1"

  if test "$REQ_TXT_TO_EDIT" = ""; then

    REQ_TXT_TO_EDIT=requirements.txt

  fi

  cp "$REQ_TXT_TO_EDIT" "$TMP_FOR_COMPARISON"

  sed -i "/egg=$PRJ_NAME/ c git+file://$(readlink -f ..)#egg=$PRJ_NAME" "$REQ_TXT_TO_EDIT"

  if cmp "$REQ_TXT_TO_EDIT" "$TMP_FOR_COMPARISON" > /dev/null ; then

    echo "sed did not change $REQ_TXT_TO_EDIT for downstream CI"

    exit 1

  fi

}

# }}}