transaction: avoid file stat ambiguity only for files in blacklist Advancing mtime by os.utime() fails for EPERM, if the target file is owned by another. bff5ccbe5ead and related changes made some code paths give advancing mtime up in such case, to fix issue5418. This causes file stat ambiguity (again), if it is owned by another. https://www.mercurial-scm.org/wiki/ExactCacheValidationPlan To avoid file stat ambiguity in such case, especially for .hg/dirstate, ed66ec39933f made vfs.rename() copy the target file, and advance mtime of renamed one again, if EPERM (see issue5584 for detail). But straightforward "copy if EPERM" isn't reasonable for truncation of append-only files at rollbacking, because rollbacking might cost much for truncation of many filelogs, even though filelogs aren't filecache-ed. Therefore, this patch introduces blacklist "checkambigfiles", and avoids file stat ambiguity only for files specified in this blacklist. This patch consists of two parts below, which should be applied at once in order to avoid regression. - specify 'checkambig=True' at vfs.open(mode='a') in _playback() according to checkambigfiles - invoke _playback() with checkambigfiles - add transaction.__init__() checkambigfiles argument, for _abort() - make localrepo instantiate transaction with _cachedfiles - add rollback() checkambigfiles argument, for "hg rollback/recover" - make localrepo invoke rollback() with _cachedfiles After this patch, straightforward "copy if EPERM" will be reasonable at closing the file opened with checkambig=True, because this policy is applied only on files, which are listed in blacklist "checkambigfiles".