tests/test-dirstate-race2.t

dirstate-v2: Add support when Rust is not enabled

This wires into `dirstatemap` the parser and serializer added in previous
changesets. The memory representation is still the same, with a flat `dict`
for `DirstateItem`s and another one for copy sources. Serialization always
creates a new dirstate-v2 data file and does not support (when Rust is not
enabled) appending to an existing one, since we don’t keep track of which
tree nodes are new or modified. Instead the tree is reconstructed during
serialization.

Differential Revision: https://phab.mercurial-scm.org/D11520

#testcases dirstate-v1 dirstate-v2

#if dirstate-v2
  $ echo '[format]' >> $HGRCPATH
  $ echo 'exp-dirstate-v2=1' >> $HGRCPATH
#endif

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