tests/test-dirstate-race2.t

tags: behave better if a tags cache entry is partially written

This is done by discarding any partial cache entry, instead of
filling the partial cache entry with 0xff before.

Differential Revision: https://phab.mercurial-scm.org/D8095

Checking the size/permissions/file-type of files stored in the
dirstate after an update where the files are changed concurrently
outside of hg's control.

  $ hg init repo
  $ cd repo
  $ echo a > a
  $ hg commit -qAm _
  $ echo aa > a
  $ hg commit -m _

  $ hg debugdirstate --no-dates
  n 644          3 (set  |unset)               a (re)

  $ cat >> $TESTTMP/dirstaterace.py << EOF
  > from mercurial import (
  >     extensions,
  >     merge,
  > )
  > def extsetup(ui):
  >     extensions.wrapfunction(merge, 'applyupdates', wrap)
  > def wrap(orig, *args, **kwargs):
  >     res = orig(*args, **kwargs)
  >     with open("a", "w"):
  >         pass # just truncate the file
  >     return res
  > EOF

Do an update where file 'a' is changed between hg writing it to disk
and hg writing the dirstate. The dirstate is correct nonetheless, and
so hg status correctly shows a as clean.

  $ hg up -r 0 --config extensions.race=$TESTTMP/dirstaterace.py
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg debugdirstate --no-dates
  n 644          2 (set  |unset)               a (re)
  $ echo a > a; hg status; hg diff