In a very rare cases there is a need to use custom license, which is not
present on the SPDX list. Now, files under such license are added to the
check_copyright ignore list. For example zigbee examples introduced
by !16205. SPDX has a LicenseRef-[idstring] identifier[1] for such cases,
so let's try to use it in license representation[2]. The idea is that licenses
not on the SPDX list can be added into the LICENSES[3] directory and used as
SPDX-License-Identifier: LicenseRef-Special-License
Or if the custom license is present directly in a source file we can use
a special LicenseRef-Included identifier to state that the license
is included.
SPDX-License-Identifier: LicenseRef-Included
Please note that LicenseRef-Included is just a made up identifier to
state the fact that the license is included directly in the source file.
There is nothing in the SPDX spec about this usage.
This relatively small adjustment allows to refer to custom licenses
without a need to skip check_copyright for them.
[1] https://spdx.github.io/spdx-spec/v2.3/other-licensing-information-detected/#101-license-identifier-field
[2] https://spdx.github.io/spdx-spec/v2.3/using-SPDX-short-identifiers-in-source-files/#e4-representing-multiple-licenses
[3] https://reuse.software/spec/
Signed-off-by: Frantisek Hrbata <frantisek.hrbata@espressif.com>
