Merge branch 'ct/diff-with-merge-base-clarification'

"git diff" used to take arguments in random and nonsense range notation, e.g. "git diff A..B C", "git diff A..B C...D", etc., which has been cleaned up. * ct/diff-with-merge-base-clarification: Documentation: usage for diff combined commits git diff: improve range handling t/t3430: avoid undefined git diff behavior