Merge branch 'tg/diff-no-index-refactor'

"git diff ../else/where/A ../else/where/B" when ../else/where is clearly outside the repository, and "git diff --no-index A B", do not have to look at the index at all, but we used to read the index unconditionally. * tg/diff-no-index-refactor: diff: avoid some nesting diff: add test for --no-index executed outside repo diff: don't read index when --no-index is given diff: move no-index detection to builtin/diff.c