twitter/bootstrap — pull request #3664 by toekneestuck (2012-06-01 03:40:51+00:00)
Title: Comma separated CSS properties with mixins (box-shadow, transition, and newly added text-shadow)

This adds the ability to pass multiple properties to the box-shadow and transition mixins (without having to pass an escaped string). It also adds a text-shadow mixin (with the same ability)

For example:

.box-shadow(1px 1px 0 rgba(0,0,0,0.5), inset -1px -1px rgba(255,255,255,0.5));

In short, when passing a single parameter to a LESS mixin with no arguments limit (e.g., using "..."), it will insert commas for every space character found. Thus, this implementation registers a default value for the second parameter (while still allowing 2+) and filters out the default value when parsing the @arguments variable.

See this post for a full description and reasoning behind the @arguments parsing and regex'ing:
http://www.toekneestuck.com/blog/2012/05/15/less-css-arguments-variable/