dirstate: make restoring from backup avoid ambiguity of file stat File .hg/dirstate is restored by renaming from backup in failure inside scopes below. If renaming keeps ctime, mtime and size of a file, restoring is overlooked, and old contents cached before restoring isn't invalidated as expected. - dirstateguard scope (from '.hg/dirstate.SUFFIX') - transaction scope (from '.hg/journal.dirstate') To avoid ambiguity of file stat at restoring, this patch invokes vfs.rename() with checkambig=True. This patch is a part of "Exact Cache Validation Plan": https://www.mercurial-scm.org/wiki/ExactCacheValidationPlan