archive: pass thru mtime for directory archives, like other archive types do

Without this files in the output archive directory have their mtimes set to
whatever time they were written their.  This is in this inconsistent with
the other archivers, eg. zip, which use exactly the same time for all files.

Works on my machine (Windows), but I don't have a *nix box available to run
anything more thorough, unfortunately.

mercurial/archival.py

@@ -262,6 +262,7 b' class fileit(object):'
     def __init__(self, name, mtime):
         self.basedir = name
         self.opener = vfsmod.vfs(self.basedir)
+        self.mtime = mtime
 
     def addfile(self, name, mode, islink, data):
         if islink:
@@ -272,6 +273,8 b' class fileit(object):'
         f.close()
         destfile = os.path.join(self.basedir, name)
         os.chmod(destfile, mode)
+        if self.mtime is not None:
+            os.utime(destfile, (self.mtime, self.mtime))
 
     def done(self):
         pass
@@ -299,7 +302,12 b' def archive(repo, dest, node, kind, deco'
 
     matchfn is function to filter names of files to write to archive.
 
-    prefix is name of path to put before every archive member.'''
+    prefix is name of path to put before every archive member.
+
+    mtime is the modified time, in seconds, or None to use the changeset time.
+
+    subrepos tells whether to include subrepos.
+    '''
 
     if kind == 'files':
         if prefix: