upgrade: update only requirements if we can Upgrade operations which involves just upgrading requirements earlier used to go through whole revlog cloning business. Now we just upgrade the requirement and skip the cloning part. Differential Revision: https://phab.mercurial-scm.org/D9775

engine: add `if True` to prepare for next patch This will help making next patch easier to read. Differential Revision: https://phab.mercurial-scm.org/D9774

test: unquiet few tests to demonstrate changes in upcoming patches Upcoming patches will skip revlog cloning for share-safe upgrades. Differential Revision: https://phab.mercurial-scm.org/D9773

upgrade: mark sharesafe improvement as only touching requirements Upgrading the repository to use share safe functionality only touches requirements. Differential Revision: https://phab.mercurial-scm.org/D9772

actions: calculate what all parts does the operation touches To make upgrade work less in certain situations, we need to teach it to find out what all parts of repository current operation is touching. This patch starts doing that. In next patch we will be setting values in improvement objects. For now, we assume everything touches everything. Differential Revision: https://phab.mercurial-scm.org/D9771

upgrade: don't create store backup if `--no-backup` is passed If the user explicitly mentioned that they don't need backup, then let's not create it. Differential Revision: https://phab.mercurial-scm.org/D9770

cext: add Python 3.10 support * Replace "Py_TYPE(obj) = type;" with "Py_SET_TYPE(obj, type);" * Add pythoncapi_compat.h header file to get Py_SET_TYPE() on Python 2.7-3.8. Header file added to mercurial/ and contrib/python-zstandard/zstd/common/. In Python 3.10, Py_TYPE(obj) must not longer be used as an l-value. pythoncapi_compat.h comes from: https://github.com/pythoncapi/pythoncapi_compat Differential Revision: https://phab.mercurial-scm.org/D9825

revlog: decouple caching from addrevision callback for addgroup For changesets, it is useful to cache the content as it will almost always be processed afterwards. For manifests on the other hand, the content is often not used directly as there is a fast path for deltas. Explicitly disable the cache in exchangev2's manifest handling for that reason. Differential Revision: https://phab.mercurial-scm.org/D9847

branchmap: update rev-branch-cache incrementally Historically, the revision to branch mapping cache was updated on demand and shared via bundle2 to avoid the cost of rebuilding on first use. Use the new `register_changeset` callback and update rbc directly on every change. Make the transfer of the bundle part redundant, but keep it for the moment to avoid the test churn. Over all, "hg unbundle" for large bundles is less than 1.8% slower for different larger repositories and that seems to a reasonable trade off. Differential Revision: https://phab.mercurial-scm.org/D9781

repository: introduce register_changeset callback The new callback is called whenever a changeset is added to the repository (commit, unbundle or exchange). Since the bulk operations already parse the changeset (readfiles or full changesetrevision), always use the latter to avoid redundant lookups. The first consumer of the new interface needs to look at extra. Differential Revision: https://phab.mercurial-scm.org/D9780