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Optionally, a path to Dockerfile can be provided. If it is empty, a default Dockerfile will be used from in a project source checkout folder is expected. If the checkout folder is empty, then a Dockerfile is expected in the root of the source folderFD_TEMP_DIR. A Dockerfile must be present to build an image. This behavior changed slightly in 5.0.3 beta. Previously, the location was expected to be in FD_TEMP_DIR/FD_PROJECT_NAME.