It is inefficient up until the point where you ask git to do a gc+repack, at which point git will look for deltas - and if it is changes to the same file, it wi

It is inefficient up until the point where you ask git to do a gc+repack, at which point git will look for deltas - and if it is changes to the same file, it will likely find them and encode them as a delta. For text files with really small changes, this is comparable to a "diff" size, and is better than what a rolling hash would achieve. However, for text files with larger changes, and of course for binary files - a rolling hash is much more effective. Additionally, a rolling hash would easily reuse cross-file similarity, where as the current delta-finding code is likely to only find redundancy in the history of the same file (or similarly named in the same directory).