If you commit 100MB file, change few bytes in it and commit it again your .git/objects will almost certainly contain two 100MB objects. The fact that it is some

If you commit 100MB file, change few bytes in it and commit it again your .git/objects will almost certainly contain two 100MB objects. The fact that it is somewhat likely that running "git gc" or something similar will convert one of them into reference to the other one and some compact representation of the difference is implementation detail. While commit object does represent the snapshot it also references the previous state, thus the commit message usually describes what was changed between the referenced snapshot and the parent(s) that are also referenced from the commit object. As for the overall model and leakage between implementation details and how people use it interesting approach is used by SCCS/BitKeeper with its internal "weave" format that essentially is both snapshot and diff at the same time.