There isn't one at the moment. The closest would be to create a pack manually that contains a diff against the previous version but that'd require manual work.

There isn't one at the moment. The closest would be to create a pack manually that contains a diff against the previous version but that'd require manual work. It would be possible, for example, to modify git-fast-import to a) allow to take diffs as input b) allow to store those diffs (these are different things to deal with). The downside is that the more packs there are, the slower object lookup is, which can make everything much slower. Newer versions of git have cross-pack indexes to deal with that, though, but I don't think that's enabled by default. Another option would be to add a new format for loose objects that allows to store diffs, but that has backwards compatibility implications.