rewriteutil: add utility to check whether empty successors should be skipped

config: add option to control creation of empty successors during rewrite The default for many history-rewriting commands (e.g. rebase and absorb) is that changesets which would become empty are not created in the target branch. This makes sense if the source branch consists of small fix-up changes. For more advanced workflows that make heavy use of history-editing to create curated patch series, dropping empty changesets is not as important or even undesirable. Some users want to keep the meta-history, e.g. to make finding comments in a code review tool easier or to avoid that divergent bookmarks are created. For that, obsmarkers from the (to-be) empty changeset to the changeset(s) that already made the changes should be added. If a to-be empty changeset is pruned without a successor, adding the obsmarkers is hard because the changeset has to be found within the hidden part of the history. If rebasing in TortoiseHg, it’s easy to miss the fact that the to-be empty changeset was pruned. An empty changeset will function as a reminder that obsmarkers should be added. Martin von Zweigbergk mentioned another advantage. Stripping the successor will de-obsolete the predecessor. If no (empty) successor is created, this won’t be possible. In the future, we may want to consider other behaviors, like e.g. creating the empty successor, but pruning it right away. Therefore this configuration accepts 'skip' and 'keep' instead of being a boolean configuration.

commands: use any() instead of `if a or b or c` Small cleanup for future when we have an option to show configs from shared rc. Differential Revision: https://phab.mercurial-scm.org/D8658

manifest: use the same logic for handling flags in _parse as elsewhere Differential Revision: https://phab.mercurial-scm.org/D8684

manifest: tigher manifest parsing and flag use In the manifest line, flags are put directly after the hash, so the parser has been guessing the presence of flags based on the length of the hash. Replace this assumption by an enumeration of the valid flags and removing them from the hash first as they are distinct input values. Consistently handle the expected 256bit length of the SHA1-replacement in the pure Python parser. Check that setting flags will use one of the blessed values. Extend write logic in the C version to handle 256bit hashes as well. Verify that hashes always have exactly the expected length. Since 1070df141718 we should no longer depend on the old extra-byte hack. Differential Revision: https://phab.mercurial-scm.org/D8679

phases: sparsify phase lists When the internal and archived phase was added, allphase became a large, sparsely populated list. This dramatically increased the number of lookup operations for public relations in `phasecache.phase`. As a first step, define allphases and related lists explicitly to contain only the actual phases. Make phasenames a dictionary and create corresponding dictionaries for mapping phase names back to numbers. Adjust various list to be sparse as well with the exception of phaseroots and phasesets members of phasecache. Keep those as a separate step as it involves changes to the C module. Differential Revision: https://phab.mercurial-scm.org/D8697

phases: updatephases should not skip internal phase Historically, updatephases used to skip the secret phase, but wasn't updated when archived and internal were added. Differential Revision: https://phab.mercurial-scm.org/D8696

repoview: use the phasecache directly to determine mutable revisions This speeds up no-change updates from 1.3s to 0.85s for my NetBSD test repository. Differential Revision: https://phab.mercurial-scm.org/D8670

phases: provide a test and accessor for non-public phase roots This decouples users from the implementation details of the phasecache. Also document a historic artifact about the stored phaseroots. Differential Revision: https://phab.mercurial-scm.org/D8694

hg-core: define a `dirstate_status` `Operation` This is 3/3 in a series of patches to improve dirstate status' code. Following in the footsteps of a46e36b82461, we move the main status functionality to an `Operation`. This will most likely be subject to change in the future (what function signature, what parameters, etc., but we will see when `rhg` gets `hg status` support. Differential Revision: https://phab.mercurial-scm.org/D8663