nodemap: track the tip_node for validation Differential Revision: https://phab.mercurial-scm.org/D8184

nodemap: add a todo list for getting out of experimental This is all the requirement I can think off. More might be added as they emerge. The first ones are mostly simple technical matters that will be taken care of soon. The question about the "status" of the persistent nodemap and the revlogs that will use it requires more discussion and thinking. Differential Revision: https://phab.mercurial-scm.org/D8181

rust-nodemap: automatically use the rust index for persistent nodemap The persistent nodemap requires the rust index to be used to provides any gains. So we automatically enable it for revlog using the persistent nodemap. We keep it off for other revset because now that the rust revlog fully initialise the nodemap using it everywhere introduce a fairly significant regression (eg: hg diff moving from 0.8s to 2.3s on mozilla-try) Differential Revision: https://phab.mercurial-scm.org/D8164