nodemap: track the maximum revision tracked in the nodemap We need a simple way to detect when the on disk data contains less revision than the index we read from disk. The docket file is meant for this, we just had to start tracking that data. We should also try to detect strip operation, but we will deal with this in later changesets. Right now we are focusing on defining the API for index supporting persistent nodemap. Differential Revision: https://phab.mercurial-scm.org/D7888

nodemap: add a flag to dump the details of the docket We are about to add more information to the docket. We first introduce a way to debug its content. Differential Revision: https://phab.mercurial-scm.org/D7887

nodemap: introduce append-only incremental update of the persistent data Rewriting the full nodemap for each transaction has a cost we would like to avoid. We introduce a new way to write persistent nodemap data by adding new information at the end for file. Any new and updated block as added at the end of the file. The last block is the new root node. With this method, some of the block already on disk get "dereferenced" and become dead data. In later changesets, We'll start tracking the amount of dead data to eventually re-generate a full nodemap. Differential Revision: https://phab.mercurial-scm.org/D7886

nodemap: keep track of the docket for loaded data To perform incremental update of the on disk data, we need to keep tracks of some aspect of that data. Differential Revision: https://phab.mercurial-scm.org/D7885

nodemap: introduce an explicit class/object for the docket We are about to add more information to this docket, having a clear location to stock them in memory will help. Differential Revision: https://phab.mercurial-scm.org/D7884

nodemap: keep track of the ondisk id of nodemap blocks If we are to incrementally update the files, we need to keep some details about the data we read. Differential Revision: https://phab.mercurial-scm.org/D7883