localrepo: restore dirstate to one before rollbacking if not parent-gone 'localrepository.rollback()' explicilty restores dirstate, only if at least one of current parents of the working directory is removed at rollbacking (a.k.a "parent-gone"). After DirstateTransactionPlan, 'dirstate.write()' will cause marking '.hg/dirstate' as a file to be restored at rollbacking. https://mercurial.selenic.com/wiki/DirstateTransactionPlan Then, 'transaction.rollback()' restores '.hg/dirstate' regardless of parents of the working directory at that time, and this causes unexpected dirstate changes if not "parent-gone" (e.g. "hg update" to another branch after "hg commit" or so, then "hg rollback"). To avoid such situation, this patch restores dirstate to one before rollbacking if not "parent-gone". before: b1. restore dirstate explicitly, if "parent-gone" after: a1. save dirstate before actual rollbacking via dirstateguard a2. restore dirstate via 'transaction.rollback()' a3. if "parent-gone" - discard backup (a1) - restore dirstate from 'undo.dirstate' a4. otherwise, restore dirstate from backup (a1) Even though restoring dirstate at (a3) after (a2) seems redundant, this patch keeps this existing code path, because: - it isn't ensured that 'dirstate.write()' was invoked at least once while transaction running If not, '.hg/dirstate' isn't restored at (a2). In addition to it, rude 3rd party extension invoking 'dirstate.write()' without 'repo' while transaction running (see subsequent patches for detail) may break consistency of a file backup-ed by transaction. - this patch mainly focuses on changes for DirstateTransactionPlan Restoring dirstate at (a3) itself should be cheaper enough than rollbacking itself. Redundancy will be removed in next step. Newly added test is almost meaningless at this point. It will be used to detect regression while implementing delayed dirstate write out.