In order to make long-lived repositories (that are never touched by the canonical Git) smaller (and to improve disk access performance and maybe to mitigate #9), the delta-compression of objects in pack files should be implemented.

Reading material can be found in the technical/ subdirectory of the Git documentation, especially pack-format.txt and pack-heuristics.txt, and, of course, in the canonical Git implementation.

Note that any delta-compression scheme adhering to the pack format should produce valid pack files, so different strategies may be tried. Caution is advised to not corrupt any Git objects... Reading all objects from the generated pack and validating their hashes is a good general test case.