#! /bin/sh
# See the discussion at https://stackoverflow.com/q/67724347/7976758

if [ -z "$1" ]; then
    echo "Usage $0 from_commit [to_commit]"
    exit 1
fi

from_commit="$1"
to_commit="${2:-HEAD}"
export from_commit to_commit

# In the superproject
{ git --no-pager diff --name-only "$from_commit" "$to_commit"

git submodule foreach '
    # In submodule "$name"
    prev_commit=`(git -C "$toplevel" ls-tree "$from_commit" "$sm_path" | awk "{print \\$3}")`
    curr_commit=`(git -C "$toplevel" ls-tree "$to_commit" "$sm_path" | awk "{print \\$3}")`
    git --no-pager diff --name-only $prev_commit $curr_commit
'; } | { test -t 1 && ${PAGER:-less} || cat -; }