Hi Ravi, I thought about that, but there's no easy way to enumerate the output from the protoc generator. It ends up generating more than one class file per input protoc, and it's not possible to determine the output file name just from the input file name.
I think CRC is also a much safer way of detecting changes, so prefer it for that reason as well. We already compute MD5s of all input files for the VersionInfo plugin too (including the proto files), so doing CRC for just the proto files shouldn't be a big overhead.
I guess one potential enhancement is sharing the checksums between the VersionInfo and Protoc plugins, but that seems reasonable to leave for future work.