view tests/test-dirstate-race.t @ 29351:bebe7d1c38c8

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

  $ hg init
  $ echo a > a
  $ hg add a
  $ hg commit -m test

Do we ever miss a sub-second change?:

  $ for i in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20; do
  >     hg co -qC 0
  >     echo b > a
  >     hg st
  > done
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a
  M a