The question is simple: How should I shorten the text of GNU GPLv3 (674 lines) for adding it to the top of all the source files in a repository?
As an example, here is a piece of text added to the top of a source file in Kdenlive repository:
/*
SPDX-FileCopyrightText: 2017 Nicolas Carion
SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
*/
Is there an appropriate format for writing such a piece of text for every source file? And is it necessary to add it to the files?