tests/test-revlog.t

bundle2: equate 'UN' with no compression

An upcoming patch will change the "alg" argument passed to this
function from None to "UN" when no compression is wanted.

The existing implementation of bundle2 does not set a "Compression"
parameter if no compression is used. In theory, setting
"Compression=UN" should work. But I haven't audited the code to see if
all client versions supporting bundle2 will accept this.

Rather than take the risk, avoid the BC breakage and treat "UN"
the same as None.

Test for CVE-2016-3630

  $ hg init

  >>> open("a.i", "w").write(
  ... """eJxjYGZgZIAAYQYGxhgom+k/FMx8YKx9ZUaKSOyqo4cnuKb8mbqHV5cBCVTMWb1Cwqkhe4Gsg9AD
  ... Joa3dYtcYYYBAQ8Qr4OqZAYRICPTSr5WKd/42rV36d+8/VmrNpv7NP1jQAXrQE4BqQUARngwVA=="""
  ... .decode("base64").decode("zlib"))

  $ hg debugindex a.i
     rev    offset  length  delta linkrev nodeid       p1           p2
       0         0      19     -1       2 99e0332bd498 000000000000 000000000000
       1        19      12      0       3 6674f57a23d8 99e0332bd498 000000000000
  $ hg debugdata a.i 1 2>&1 | egrep 'Error:.*decoded'
  (mercurial.mpatch.)?mpatchError: patch cannot be decoded (re)