Remote code execution when cloning a malicious Git, Mercurial or SVN repository

  A "ssh://..." URL can result in a "ssh" command line with a
  hostname that begins with a dash "-", which would cause the 
  "ssh" command to instead (mis)treat it as an option. This is 
  now prevented by forbidding such a hostname (which should
  not impact any real-world usage).

Why not simply use "--", which is the standard way to separate option from non-option arguments? OpenSSH uses getopt(3) and so fully supports this behavior, as should any other correctly written utility. At the very least, "--" should be used in addition to hostname filters.