vimrc: set diffopt(s)

.vim/vimrc

@@ -731,6 +731,11 @@ set wildignore+=*.spl                            " compiled spelling word lists
 set wildignore+=*.pyc                            " Python byte code
 set wildignore+=node_modules/**
 set wildmode=longest:longest,full
+
+" filler lines to keep text position; start diff with vertical splits; don't
+" ignore case and whitespace changes
+set diffopt=filler,vertical
+
 set scrolloff=5               " scroll offset, min lines above/below cursor
 "set scrolljump=5             " jump 5 lines when running out of the screen - NO
 set sidescroll=10             " minimum columns to scroll horizontally