dirstate: ignore stat data for files that were updated too recently

This should fix the race where

  hg commit foo
  <change foo without changing its size>

happens in the same second and status is fooled into thinking foo
is clean.

A configuration item is used to determine the timeout, since different
filesystems may have different requirements (I think VFAT needs 3s,
while most Unix filesystems are fine with 1s).

mercurial/dirstate.py

@@ -10,7 +10,7 b' of the GNU General Public License, incor'
 from node import nullid
 from i18n import _
 import struct, os, bisect, stat, strutil, util, errno, ignore
-import cStringIO, osutil
+import cStringIO, osutil, sys
 
 _unknown = ('?', 0, 0, 0)
 _format = ">cllll"
@@ -66,6 +66,12 b' class dirstate(object):'
         elif name == '_checkexec':
             self._checkexec = util.checkexec(self._root)
             return self._checkexec
+        elif name == '_limit':
+            try:
+                self._limit = int(self._ui.config('ui', 'limit', 1))
+            except ValueError:
+                self._limit = 1
+            return self._limit
         else:
             raise AttributeError, name
 
@@ -335,6 +341,11 b' class dirstate(object):'
     def write(self):
         if not self._dirty:
             return
+        st = self._opener("dirstate", "w", atomictemp=True)
+        if self._limit > 0:
+            limit = util.fstat(st).st_mtime - self._limit
+        else:
+            limit = sys.maxint
         cs = cStringIO.StringIO()
         copymap = self._copymap
         pack = struct.pack
@@ -343,10 +354,11 b' class dirstate(object):'
         for f, e in self._map.iteritems():
             if f in copymap:
                 f = "%s\0%s" % (f, copymap[f])
+            if e[3] > limit and e[0] == 'n':
+                e = (e[0], 0, -1, -1, 0)
             e = pack(_format, e[0], e[1], e[2], e[3], len(f))
             write(e)
             write(f)
-        st = self._opener("dirstate", "w", atomictemp=True)
         st.write(cs.getvalue())
         st.rename()
         self._dirty = self._dirtypl = False

tests/test-filebranch.out

@@ -3,10 +3,10 b' 4 files updated, 0 files merged, 0 files'
 creating branch a
 creating branch b
 we shouldn't have anything but n state here
-n 644          2 bar
-n 644          3 baz
-n 644          3 foo
-n 644          2 quux
+n   0         -1 bar
+n   0         -1 baz
+n   0         -1 foo
+n   0         -1 quux
 merging
 pulling from ../a
 searching for changes

tests/test-rebuildstate.out

@@ -2,7 +2,7 b' adding bar'
 adding foo
 % state dump
 a   0         -1 baz
-n 644          0 foo
+n   0         -1 foo
 r   0          0 bar
 % status
 A baz