test: add test for a former race resulting in bad dirstate

In 6.0 this used to result in the size being stored in the dirstate is wrong.
This was fixed by other change to the mtime gathering logic.

Differential Revision: https://phab.mercurial-scm.org/D11749

tests/test-dirstate-race2.t

@@ -1,54 +1,89 b''
 #testcases dirstate-v1 dirstate-v2
 
 #if dirstate-v2
   $ cat >> $HGRCPATH << EOF
   > [format]
   > exp-rc-dirstate-v2=1
   > [storage]
   > dirstate-v2.slow-path=allow
   > EOF
 #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 _
 # this sleep is there to ensure current time has -at-least- one second away
 # from the current time. It ensure the mtime is not ambiguous. If the test
 # "sleep" longer this will be fine.
 # It is not used to synchronise parallele operation so it is "fine" to use it.
   $ sleep 1
   $ hg status
 
   $ hg debugdirstate --no-dates
   n 644          3 (set  |unset)               a (re)
 
   $ cat >> $TESTTMP/dirstaterace.py << EOF
+  > import time
   > from mercurial import (
+  >     commit,
   >     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
+  >     extensions.wrapfunction(merge, 'applyupdates', wrap(0))
+  >     extensions.wrapfunction(commit, 'commitctx', wrap(1))
+  > def wrap(duration):
+  >     def new(orig, *args, **kwargs):
+  >         res = orig(*args, **kwargs)
+  >         with open("a", "w"):
+  >             pass # just truncate the file
+  >         time.sleep(duration)
+  >         return res
+  >     return new
   > 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
+
+Do a commit where file 'a' is changed between hg committing its new
+revision into the repository, and the writing of the dirstate.
+
+This used to results in a corrupted dirstate (size did not match committed size).
+
+  $ echo aaa > a; hg commit -qm _
+  $ hg merge -qr 1; hg resolve -m; rm a.orig
+  warning: conflicts while merging a! (edit, then use 'hg resolve --mark')
+  (no more unresolved files)
+  $ cat a
+  <<<<<<< working copy: be46f74ce38d - test: _
+  aaa
+  =======
+  aa
+  >>>>>>> merge rev:    eb3fc6c17aa3 - test: _
+  $ hg debugdirstate --no-dates
+  m   0         -2 (set  |unset)               a (re)
+  $ hg commit -m _ --config extensions.race=$TESTTMP/dirstaterace.py
+  $ hg debugdirstate --no-dates
+  n   0         -1 unset               a
+  $ cat a | wc -c
+   *0 (re)
+  $ hg cat -r . a | wc -c
+   *105 (re)
+  $ hg status; hg diff --stat
+  M a
+   a |  5 -----
+   1 files changed, 0 insertions(+), 5 deletions(-)