This option will allow to pull changesets that are hidden on the remote. This
is useful when looking into a changeset’s evolution history, resolving
evolution instability or mirroring a repository.

The option is best effort and will only affect the pull when it can. The option
will be ignored when it cannot be honored.

Support for each type of peer is yet to be implemented. They currently all warn
about lack of support. The warning code will get removed as peers gain
support for this option.

The option is still experimental, so we will have freedom to update the UI or
implementation before it graduates out of experimental.

Based on a changeset by Pierre-Yves David, which added the option.