Copy changesets from a local repository instance to a remote one.

The push operation is used for synchronization between two repository instances. Specifically, this operation happens from the perspective of a local repository instance that wants to copy some changesets into a remote instance. Usually, the remote instance is the one from which the local instance was originally cloned.

Note that the two repository instances are not necessarily identical after the push. We may have constrained the push by instructing the VCS to only send some of the local changes. Or the remote instance may contain things that are not in the local instance.