first pass at dockerfile support

plugins/common/functions

@@ -85,9 +85,16 @@ dokku_log_fail() {
 verify_app_name() {
   local APP="$1"
   [[ ! -d "$DOKKU_ROOT/$APP" ]] && dokku_log_fail "App $APP does not exist"
+  IMAGE="dokku/$APP"
   return 0
 }
 
+is_image_buildstep_based() {
+  # circleci can't support --rm as they run lxc in lxc
+  [[ ! -f "/home/ubuntu/.circlerc" ]] && local DOCKER_ARGS="--rm"
+  docker run --entrypoint="/bin/bash" $DOCKER_ARGS "$@" -c "[[ -f /exec ]]"
+}
+
 parse_args() {
   for arg in "$@"; do
     case "$arg" in