branching: merge stable into default This show that the recent changes on default fixed the issue with transaction overwriting content in `test-transaction-wc-rollback-race.t`

transaction: tests we don't overwrite bookmark activation on abort We actually do not! Great.

transaction: tests we don't overwrite updates on abort spoiler: we do… /o\

transaction: tests we don't overwrite branch changes on abort We actually do not! Great. …Why are doing a backup of the `branch` files at transaction creation then‽

transaction: tests we don't overwrite tracking to changed file on abort spoiler: we do…

transaction: the base of a new test file checking transaction abort issue See inline documentation for details. See other changesets for actual cases.

setup: support building from an ongoing merge Before this change the two parents from the merge would duplicate some command output and modify some others in a way python 3.11 chokes on.

rhg: in path_encode, simplify a bit more Use the slices for `basename` and `ext` instead of dealing with offsets.

rhg: in path_encode, be a bit more conservative about memory usage Use [shrink_to_fit] to match the previous behavior more closely, and potentially save (a tiny bit) of memory. FWIW, I suspect this is unnecessary, but this whole MR is about simplifying things while preserving any existing optimizations.

rhg: small refactor: stop using a magical constant "+ 1" Instead, directly do what the "+ 1" was supposed to achive: call hash_encode.