commit https://github.com/vim/vim/commit/24db72958fc91bd067c7d60a4990d09a6f295b48 Author: Bram Moolenaar <Bram@vim.org> Date: Sun Jan 3 16:56:10 2016 +0100 patch 7.4.1040 Problem: The tee command is not available on MS-Windows. Solution: Adjust tee.c for MSVC and add a makefile. (Yasuhiro Matsumoto)

" Settings for test script execution
" Always use "COMMAND.COM", don't use the value of "$SHELL".
set shell=c:\COMMAND.COM shellquote= shellxquote= shellcmdflag=/c shellredir=>
" This is used only when the +eval feature is available.
if executable("cmd.exe")
   set shell=cmd.exe
endif