Sink is a data access layer handling synchronization, caching and indexing.
Discussion of the code should be done on the kde-pim at kde.org mailing list or in #kontact on IRC.
Note that all feature development should happen in feature branches, and that the mainline development branch is "develop". Master is for releases. It is recommended (though not required) to use the "git flow" tools to make branched development easy (and easy for others to coordinate with).
For further information on the project see the KDE Phabricator instance.
This documentation is built using mkdocs.org.
mkdocs serve to run a local webserver to view the docs.
The documentation is also published at http://api.kde.org/doc/sink/ and rebuilt nightly.