Can Mercurial be made to preserve file permissions?

I've seen a number of blog posts, and have experienced for myself, that Mercurial does not preserve the permissions on files pushed from one repo to another. Does anyone know of a Mercurial extension that would preserve the permissions? I'm assuming it can't be done with a hook, because what does a hook know about permissions at the originating repo?

Requested elaboration:

• If the only change to a file is a change in permissions (e.g., chmod o+r filename), attempts to commit the file fail with a message saying that the file has not changed.

• If I commit a file with permissions 600 (rw-------), then clone the repo, the same file in the clone has permissions 664 (rw-rw-r--):

  : nr@yorkie 6522 ; hg clone one two
  updating working directory
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  : nr@yorkie 6523 ; ls -l one two
  one:
  total 4
  -rw------- 1 nr nr 8 Aug 18 21:50 foo
  
  two:
  total 4
  -rw-rw-r-- 1 nr nr 8 Aug 18 21:51 foo
  

This examples shows that hg clone does not preserve permissions, but hg push does not preserve them either.

In my application, one repo is on a publically accessible path, and it's of major importance that

• Multiple users have the right to change the repo

• Files in the public repo become readable only when explicitly made readable.