Filtering of git repository

Actually, the default reflog expire time is 90 days. It's unreachable commits that have a default 30 days expire time.

Yes, but the old commits _will_ be unreachable once you have pulled all refs and fixed your own local branches.

Anyway, the blobs ought to be mostly the same, so I don't think the old history takes that much more space. Haven't measured it, though.

About 50% more, according to my measurements, if you repack everything.

Note that old stashes also keep references to the old history. So if one wants to get rid of it then it's necessary to pop each stash into the new branches and stash them again.

Good catch, I hadn't thought about stashes.