Copying vs of cloning?

[Andrei Gaponenko]

Hi,

If one copies a Mercurial repository (with "cp -pr", or using tar), is
the copy a valid repository?   I thought that after

    cd /someplace
    hg clone /a/parent/repo

copying the newly created repo to /otherplace would be equivalent to

    cd /otherplace
    hg clone /a/parent/repo

However running "diff -r" on two such clones I see that their
.hg/dirstate files differ.  If I copied repo instead of cloning they
would be identical.  So copying does not seem to be equivalent to
cloning.

What is the difference???

Regards,
Andrei