Does git have a concept of log compaction?

The git version control system, is a kind of distributed log (with some conceptual similarities to the raft consensus protocol).

Raft and some other systems have a concept of log compaction, so new clients don't need to traverse the whole change set to apply changes.

My question is: Does git have a concept of log compaction?

new clients don't need to traverse the whole change set to apply changes.

No, git is a collection of snapshots (full copy of a working tree).
When you access a commit in git, you don't have to traverse the all log or history to build its content.

See "How does git store files?": the internal storage does use delta in pack files (that is form of "compaction", not just "log compaction"), but each commit still represents the full working tree.

Every time you commit, or save the state of your project in Git, it basically takes a picture of what all your files look like at that moment and stores a reference to that snapshot.
To be efficient, if files have not changed, Git doesn’t store the file again—just a link to the previous identical file it has already stored.