twitter/bootstrap — pull request #2775 by bartt (2012-03-23 19:46:29+00:00)
Title: In LESS 1.3.0 the number of arguments matter

The native box-shadow, background-clip and background-size instructions all take 1 or more arguments. In 1.3.0 LESS became arity aware, see https://gist.github.com/1933613. As a result the signatures of these mixins had to change a little.