How to find out which files take up the most space in git repo?

twalberg’s answer does the trick. I wrapped it up in a loop so that you can list files in order by size:

while read -r largefile; do
    echo $largefile | awk '{printf "%s %s ", $1, $3 ; system("git rev-list --all --objects | grep " $1 " | cut -d \" \" -f 2-")}'
done <<< "$(git rev-list --all --objects | awk '{print $1}' | git cat-file --batch-check | sort -k3nr | head -n 20)"

head -n 20 restricts the output to the top 20. Change as necessary.

Once you’ve identified the problem files, check out this answer for how to remove them.