This is a port of the diff part of Neil Fraser's diff_match_patch to Go, derived from the Java implementation. All diff-related tests have been ported too.

The implementation is based on processing items of type string. An utility package ./rstring, which is partly based on Go standard package exp/utf8string, helps navigating runewise (rather than bytewise). Perhaps it would be preferable to use []rune instead of string, but this hasn't been tried yet.

Measured in 2012, the performance on a i386 system was between that of the Java and the Qt based C++ implementations. On amd64 systems the Go port performed as fast as the Java implementation (the 6g compiler is able to generate faster code than 8g, because of the larger number of available registers on 64bit processors).