magnars/s.el — pull request #17 by pd (2012-12-17 21:27:24+00:00)
Title: s-match: support optional capture groups

The values of match-data do not seem to support the ideal case. For the
test of "(abc)(def)?" matching against "abc", the most reasonable result
would be ("abc" "abc" nil); however, match-data provides no indication
of the second capture group.

Without this, though, s-match errors when match-data contains nils.