Both emacs and vim can be run under windows, and both have the ability to display 3-way merges quite well. For emacs, you'd want magit + smerge or ediff. In v

Both emacs and vim can be run under windows, and both have the ability to display 3-way merges quite well. For emacs, you'd want magit + smerge or ediff. In vim, you'd want vimdiff + vim-fugitive for a few handy helpers.