Test data was taken from the Go distribution, which was in turn taken from the 
testregex test suite:

  http://www2.research.att.com/~astopen/testregex/testregex.html

The LICENSE in this directory corresponds to the LICENSE that the data was
released under.

The tests themselves were modified for RE2/Go. A couple were modified further 
by me (Andrew Gallant) (only in repetition.dat) so that RE2/Go would pass them. 
(Yes, it seems like RE2/Go includes failing test cases.) This may or may not 
have been a bad idea, but I think being consistent with an established Regex 
library is worth something.

Note that these files are read by 'src/etc/regexp-match-tests' and turned into 
Rust tests found in 'src/libregexp/tests/matches.rs'.