revlog: add a function to build index entry tuple Keeping index entry as tuple make sense for performance reason, however it does not means we need to manually build that tuple for all piece of python code that are not performance critical. So we add a nice function responsible to build the tuple using argument using explicit keyword argument. Differential Revision: https://phab.mercurial-scm.org/D10793

revlog: move `offset_type` to `revlogutils` This multiple module are using this so it make sense to move it at the utility level. Differential Revision: https://phab.mercurial-scm.org/D10792

revlog: move entry documentation alongside new related constants Accessing individual index-entry element is usually done using integer directly. This is presumably for "performance reasons". However as the index entry gain more and more element it seems useful to get the option to use symbolic constant to access item, for both clarify and versatility. We will probably keep using integer for performance critical path, but less critical code may start using them now that they are declared. Differential Revision: https://phab.mercurial-scm.org/D10791

censor: drop size limitation on the tombstone This limitation seems to date back from a previous implementation of censors, were the revision were censored" in place. For a long while the implementation actually involved rewriting the revlog before replacing the original data. So it looks like we can safely remove this limitation. The tests suite agrees. Differential Revision: https://phab.mercurial-scm.org/D10790

revlog: move censoring code in a dedicated module This code is quite specific and we are about to add more of it for revlog-v2 (and other derived version). So we move this code in a dedicated module in `mercurial/revlogutils/`. This looks like a good fit. The diff is huge because I used `hg copy` to create the new file so that we keep the history of the censor code. Differential Revision: https://phab.mercurial-scm.org/D10789

censor: reduce risk of censor test blowing up output limit The censored file is really big, and we keep using `hg cat` on it, with the assumption that it is censored. However, when it is not censored, the amount of extra line output is huge and quickly saturate the backlog of terminal and CI system. Differential Revision: https://phab.mercurial-scm.org/D10788

revlog: store sidedata in their own file This makes sidedata manipulation simpler and results in more compact data when traversing either data or sidedata. Differential Revision: https://phab.mercurial-scm.org/D10787

revlog: fix docket.date_filepath docstring This was copy-pasted too quickly. Differential Revision: https://phab.mercurial-scm.org/D10786

revlog: use dedicated code for reading sidedata We are about to introduce a new, dedicated, file to store sidedata. Before doing so, we make sidedata reading go through different code as reading data chunk. This will simplify some of the complexity of the next changesets. The reading is very simple right now and will need some improvement later to reuse some of the caching strategy we use for the data file. Differential Revision: https://phab.mercurial-scm.org/D10785

revlog: simplify "partial read" error message We are about to reuse this message in more places and the current handling is pretty hard to read. So we eat two pie with one stone and clean up this. Differential Revision: https://phab.mercurial-scm.org/D10784