Karl Fogel <[email protected]> writes: > Now, how hard would this be to actually implement?
To have a more or less accurate estimate, I went ahead and prepared the first-cut implementation of an approach that makes the pristine checksum kind configurable in a working copy. The current implementation passes all tests in my environment and seems to work in practice. It is available on the branch: https://svn.apache.org/repos/asf/subversion/branches/pristine-checksum-kind The implementation on the branch allows creating working copies that use a checksum kind other than SHA-1. The checksum kind is persisted in the settings table. Upgraded working copies of the older formats will have SHA-1 recorded as their pristine checksum kind and will continue to use it for compatibility. Newly created working copies of the latest format (with --compatible-version=1.15 or --store-pristine=no), as currently implemented, will use the new pristine checksum kind. Currently, as a proof-of-concept, the branch uses salted SHA-1 as the new pristine checksum kind. For the production-ready state, I plan to support using multiple new checksum types such as SHA-256. I think that it would be useful for future compatibility, because if we encounter any issues with one checksum kind, we could then switch to a different kind without having to change the working copy format. One thing worth noting is that ra_serf contains a specific optimization for the skelta-style updates that allows skipping a GET request if the pristine store already contains an entry with the specified SHA-1 checksum. Switching to a different checksum type for the pristine entries is going to disable that specific optimization. Re-enabling it would require an update of the server-side. I consider this to be out of scope for this branch. I can complete the work on this branch and bring it to a production-ready state, assuming there are no objections. Thanks, Evgeny Kotkov
