dirstate-item: keep the full information in memory (for pure form) This changeset is finally reaching the area where we have been headed this whole time. Since all implementation details are contained inside de DirstateItem logic, we can change the way it is implemented. So we store the information that are passed to the object and use them to dynamically compute the "legacy" value. For now we only do this for the Pure implementation, as this is a good demonstration for the logic is fully insulated. The next step will be the update the C code too, to implement the various method with the new attribute (instead of the legacy one) and then start seriously thinking about the parameters we feed into DirstateItem. Differential Revision: https://phab.mercurial-scm.org/D11364