clone: process 'lookup' return as an arbitrary symbol In theory, checkout is expected to be a node here because it was returned by peer.lookup. In practice, multiple important extensions (like hg-git, hg-subversion) use peers not backed by a mercurial repository where lookup cannot return a node. Allowing arbitrary symbols is necessary to make these extensions working with 4.7. We should probably introduce a new API in Core to have these extensions to work without abusing the lookup API. In the meantime, a small change to restore compatibility in 4.7 seems in order.