nodemap: all check that revision and nodes match in the nodemap More check is always useful. Differential Revision: https://phab.mercurial-scm.org/D7846

nodemap: add basic checking of the on disk nodemap content The simplest check it so verify we have all the revision we needs, and nothing more. Differential Revision: https://phab.mercurial-scm.org/D7845

nodemap: code to parse the persistent binary nodemap data We now have code to read back what we persisted. This will be put to use in later changesets. Differential Revision: https://phab.mercurial-scm.org/D7844

nodemap: move the iteratio inside the Block object Having the iteration inside the serialization function does not help readability. Now that we have a `Block` object, let us move that code there. Differential Revision: https://phab.mercurial-scm.org/D7843

nodemap: use an explicit "Block" object in the reference implementation This will help us to introduce some test around the data currently written on disk. Differential Revision: https://phab.mercurial-scm.org/D7842

nodemap: add a optional `nodemap_add_full` method on indexes This method can be used to obtains persistent data for a full nodemap. The end goal is for some index implementation to managed the nodemap serialization them selves (eg: the rust implementation) Differential Revision: https://phab.mercurial-scm.org/D7841