util: extract stub function to get mtime with second accuracy

This function is trivial but will need a long comment why it can't use
st.st_mtime. See the next patch for details.

mercurial/context.py

@@ -1690,7 +1690,7 b' class workingfilectx(committablefilectx)'
     def date(self):
         t, tz = self._changectx.date()
         try:
-            return (int(self._repo.wvfs.lstat(self._path).st_mtime), tz)
+            return (util.statmtimesec(self._repo.wvfs.lstat(self._path)), tz)
         except OSError as err:
             if err.errno != errno.ENOENT:
                 raise

mercurial/dirstate.py

@@ -428,7 +428,7 b' class dirstate(object):'
     def normal(self, f):
         '''Mark a file normal and clean.'''
         s = os.lstat(self._join(f))
-        mtime = int(s.st_mtime)
+        mtime = util.statmtimesec(s)
         self._addpath(f, 'n', s.st_mode,
                       s.st_size & _rangemask, mtime & _rangemask)
         if f in self._copymap:
@@ -998,7 +998,7 b' class dirstate(object):'
             if not st and state in "nma":
                 dadd(fn)
             elif state == 'n':
-                mtime = int(st.st_mtime)
+                mtime = util.statmtimesec(st)
                 if (size >= 0 and
                     ((size != st.st_size and size != st.st_size & _rangemask)
                      or ((mode ^ st.st_mode) & 0o100 and checkexec))

mercurial/util.py

@@ -952,6 +952,9 b' def fstat(fp):'
     except AttributeError:
         return os.stat(fp.name)
 
+def statmtimesec(st):
+    return int(st.st_mtime)
+
 # File system features
 
 def checkcase(path):