No-op reconciliations are very inefficient, as they carry out
a full clone operation of the target repository even when
no changes have taken place.
This change will execute a remote-ls operation, and cancel
the clone operation if the remote tip commit is still the same
as the one observed on the last reconcilation. In such cases,
an git.NoChangesError is returned.
Signed-off-by: Paulo Gomes <paulo.gomes@weave.works>
860d7051da