tests: demonstrate a bug in dirstate-v2 handling of errors

tests: add a rewriting step to detect EACCES errors

undo-files: cleanup legacy files when applicable The "journal" code is much more compact in 6.4, and so is the "undo" files as a result. However the previous version were much noisier, so let us cleanup undo files from older version too.

undo-files: clean existing files up before writing new one the in the initial design of journal/undo interaction, ages ago, new file always overwrote previous files. This is no longer the case for a long while, so it is time to properly clean things up before writing new ones. Otherwise, inconsistent "undo" state might exist on disk, leading `hg rollback` to misbehave (more that intended).

undo-files: make the undo-prefix configurable in `cleanup_undo_files` The transaction is configuration undo prefix, so we "need" it too.

undo-files: no longer pass the `repo` to `cleanup_undo_files` As foretold in the previous changesets, we no longer need a full repository object here.

undo-files: relies on a explicit list of possible undo files Instead of infering the list of undo files from the `_journalfiles` method on `localrepository`, we explicitly have the list of file in a constant next to the cleanup code. In practice this does not change much as `_journalfiles` is already returning the same "static" list and no internal or extensions extensions seems to actually wrap that. In addition, that list is not "too short" for cleanup, in case we need to cleanup undo files from older version of Mercurial that used to use more of them. this will be dealt with in a later changesets. This change is a step toward our goal to use the `cleanup_undo_files` within the transaction. The transaction has no reference to the `repo` object, so we need to move toward `cleanup_undo_files` not having one either.

undo-files: move the undo cleanup code in the transaction module Now that undo creation is gathered in the transaction module, let us move the code cleaning them up there too. This will be useful to better clean previous undo files up before creating new ones.

undo-files: drop the old undo rename logic It is no longer necessary I am not changing the transaction.__init__ signature since we are on stable right now.

undo-files: have the transaction directly tracks and manages journal rename This is much simpler this way.

undo-files: add a undoname closure to the _write_undo method We will also needs it when the transaction will take care of the other journal files, which is soon™.

undo-files: cleanup backup when cleaning undos Previously, the backups were left behind, by operation cleaning the undo's like strip, narrow and stream clone. The remaining elevant in the room is the transaction itself, who does not properly cleanup undo backup before copying the new ones.

undo-files: factor the vfs map in a repository property We define it in multiple locations and inconsistencies are appearing. So we now have a single definition point.

undo-files: add a utility function to read the backup-files definition We will need it in multiple places. so lets factor the logic around.

undo-files: use the cleanup function in streamclone Lets use the same code, so that we can fix things only once.

undo-files: also remove the undo.backupfiles The undo.backupfiles is dealt is directly managed by the transaction instead of going through the `localrepo.undofiles`. We start doing minimal management for it before using `cleanup_undo_files` on more situation. Proper handling of it is an intermediate goal of this series.

undo-files: use the cleanup function in narrow Lets use the same code, so that we can fix things only once.

undo-files: extract the cleanup code from strip in a function This logic is duplicated in multiple places and it missing some important parts. So lets start dealing with the duplication first.

run-tests: fix a crash when using the coverage options 35bf7f23b84c attempted to transition away from `distutils`, but the `packaging` code lacks `StrictVersion`. I have no idea when `packaging.version` became available, but I have it in python 3.6, so that should be good enough. For some reason, the import checker thinks this is a local import, and needs help to decide otherwise. Alternately we could ditch the version check entirely, because `coverage` is currently at 7.2.1, and the original check was added back in 2010.

rust: fix building on macOS (issue6801) The VFS change is copied over from Cargo, and likely to apply to other platforms as well. The dirstate change is essentially a replay of 440972d2175d, which was reverted in e98fd81bb151, part of !383, to silence some clippy warnings.

tests: fix timeout adjustement in delaypush.py Doing integer arithmetic with string is bound to fail.

relnotes: add 6.4 and empty next

Added signature for changeset 05de4896508e

Added tag 6.4rc0 for changeset 05de4896508e