contrib: install Rust 1.46.0 Let's use the latest/greatest version of Rust in the automation environment. Differential Revision: https://phab.mercurial-scm.org/D9146

contrib: install latest versions of Python Let's keep our build environment modern. We upgrade 3.5-3.8 on Linux. Just 3.7 and 3.8 on Windows because we don't use <3.7 on Windows. Differential Revision: https://phab.mercurial-scm.org/D9145

help: extract logic for listing commands and topics Differential Revision: https://phab.mercurial-scm.org/D9134

copies: directly pass a changes object to the copy tracing code The object contains all the data we need. For example, the `is_merged` callback can now use the associated precomputed data. This will be useful again soon when the `salvaged` set will be introduce to solve the issue with delete file reverted during a merge. See 4b582a93316a and 14be07d5603c for details. Differential Revision: https://phab.mercurial-scm.org/D9117

copies: no longer change the sidedata flag With the new sidedata storage that include data about all file changes, every revision has one, so the sidedata flag is not longer a good way to spot changeset with copy information. So we drop this check to simplify the code We optimisation itself provided an interesting speedup, so we will likely reintroduce something similar, with a dedicated flag, in the future. Differential Revision: https://phab.mercurial-scm.org/D9116

copies: use dedicated `_revinfo_getter` function and call We want to return data in a different form, so we need different revinfo function. At that point it make sense to have different getter. Differential Revision: https://phab.mercurial-scm.org/D9115

copies: make two version of the changeset centric algorithm They are two main ways to run the changeset-centric copy-tracing algorithm. One fed from data stored in side-data and still in development, and one based on data stored in extra (with a "compatibility" mode). The `extra` based is used in production at Google, but still experimental in code. It is mostly unsuitable for other users because it affects the hash. The side-data based storage and algorithm have been evolving to store more data, cover more cases (mostly around merge, that Google do not really care about) and use lower level storage for efficiency. All this changes make is increasingly hard to maintain de common code base, without impacting code complexity and performance. For example, the compatibility mode requires to keep things at different level than what we need for side-data. So, I am duplicating the involved functions. The newly added `_extra` variants will be kept as today, while I will do some deeper rework of the side data versions. Long terms, the side-data version should be more featureful and performant than the extra based version, so I expect the duplicated `_extra` functions to eventually get dropped. Differential Revision: https://phab.mercurial-scm.org/D9114

changing-files: retrieve changelogrevision.files from the sidedata block The `files` field is know to have issue, using a list with fixed, and fixable, computation can only help. For example, using a fixes `files` field would be enough to fix issue6219 once this feature get usable in production. We focus on having thing working for now, we will deal with performance later. Right now we have a ironic situation were we parse sorted value from disk to turn them into a set and then having to sort it again. Differential Revision: https://phab.mercurial-scm.org/D9092

changing-files: drop the now useless changelogrevision argument Since all filename are now included in the sidedata block, we no longer need to decode the `files` from the revision. Differential Revision: https://phab.mercurial-scm.org/D9091

changing-files: rework the way we store changed files in side-data We need to store new data so this is a good opportunity to rework this fully. 1) We directly store the list of affected file in the side data: * This avoid having to fetch and parse the `files` list in the revision in addition to the sidedata. Making the data more self sufficient. * This work around situation where that `files` field contains wrong information, and open the way to other bug fixing (eg: issue6219) * The format (fixed initial index, sorted files) allow for fast lookup of filename within the structure. * This unify the storage of affected files and copies sources and destination, limiting the number filename stored redundantly. * This prepare for the fact we should drop the `files` as soon as we do any change affecting the revision schema. * This rely on compression to avoid a significant increase of the changelog.d. More testing on this will be done before we freeze the final format. 2) We can store additional data: * The new "merged" field, * A future "salvaged" set recording files that might have been deleted but have were still present in the final result. Differential Revision: https://phab.mercurial-scm.org/D9090