Git pre-commit hook that rejects commits that are too large

pre-commit-check-git-commit-size.sh

#!/usr/bin/env bash -eou pipefail

# https://www.backblaze.com/blog/how-many-bytes-are-in-a-megabyte-really/
size_limit=$((2 * 2**20)) # 2mbs
# https://git-scm.com/docs/git-rev-list#Documentation/git-rev-list.txt---disk-usage
commit_size=$(git rev-list --disk-usage HEAD^..HEAD)

test "$commit_size" -lt "$size_limit" || (
  echo "Commit size is too large: $commit_size > $size_limit"
  echo "Force commit using --no-verify"
  exit 1
)

I'm getting this error message:

Git: fatal: Invalid revision range HEAD^..HEAD

Do you have any idea why?

@simonseo Yes, I am guessing that your repo doesn't have more than 2 commits?