Specify link to Github, BitBucket or GitLab as requirement for `url` field

[arduino]

Specify link to Github, BitBucket or GitLab as requirement for `url` field

[per1234]

Hi @aliphys. Thanks for your suggestion.

According to the library registery FAQ:

- [ ] The library repository must be hosted on a major Git-hosting website like GitHub, BitBucket or GitLab (other hosting sites may be considered on request).

That requirement is about the URL that is added to the repositories.txt file in the arduino/library-registry repository. The reason for the restrictions on that URL is because the libraries-repository-engine tool must be able to check out the library's Git repository in order to generate the Library Manager index and associated assets.

Since this data is not part of the Arduino library project content, a separate tool is used to check the Library Manager submissions for compliance with this requirement:

https://github.com/arduino/library-registry-submission-parser/blob/1.1.1/main.go#L272-L279

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The purpose of the url field of the library.properties metadata file is to provide the library user with a link they can follow to get more information about the library. The library repository might be the place where that information is found, but this is not required. In fact, many of the official Arduino libraries use the URL of the library's page in the Arduino Library Reference (example), and that is perfectly fine (and in fact superior for the purpose when compared to sending the end user directly to the repository). So there is no need to apply the same requirements on the url field of the library.properties file as we impose on the registration URL.