Do we have a documentation for packages.json - field source?

[matjung]

Hello Getcomposer Authors and Community
https://getcomposer.org/doc/05-repositories.md#packages

Extract from documentation:
The @composer.json marker would be the contents of the composer.json from that package version including as a minimum:
name
version
dist or source

I try to find the documentation for the source field.

[Seldaek]

See #219 (comment)