This appears to solve the problem with vagrant-1.8.1 on Windows 7 x64 in a git-bash 2.7.2 shell with rsync.exe copied from an msys2 installation into /mingw64/bin/rsync.

@sethvargo Can we please get this merged? This is a dealbreaker for Windows users.

Does this address the issue for cygwin? For window hosts and bsd guests rsync is only viable/easy way

Did this solve the issue? Previously I would remove the 3 options in lines 77-79 from the helper.rb (which worked). When I upgraded to 1.8.5, I saw the changes to the helper.rb file, and it looks like it should detect the host and when it's a Windows host the 3 problematic options are removed.

So I thought it would work, but the issue persisted. Reverting back to 1.8.4 with those lines removed fixed the issue again.

Vagrant 1.8.5 has been working great for me with rsync in Windows.

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