git-cherry-diff.sh

#!/usr/bin/env bash

set -euo pipefail



if [[ $# -eq 2 ]]; then
    upstream="$1"
    topic="$2"
elif [[ $# -eq 1 ]]; then
    upstream="$1"
    topic="HEAD"
else
    # assumptions on both remote and default branch
    upstream="github/master"
    topic="HEAD"
fi

# shellcheck disable=SC2207
naive_list=( $(git log "$upstream"..."$topic" --no-merges --pretty=%H) )
if [[ ${#naive_list[@]} -eq 0 ]]; then
    exit 0
fi

last_commit=${naive_list[ (${#naive_list[@]} - 1) ]}
last_commit_time=$(git show -s --format=%ci "$last_commit")

# shellcheck disable=SC2207
since_list=( $( git log "$upstream" --oneline --after "$last_commit_time" --no-merges --pretty=%H ) )
if [[ ${#since_list[@]} -eq 0 ]]; then
    since_patches="null"
else
    since_patches=$(for hash in "${since_list[@]}"; do
        git show --patch-with-raw "$hash" | git patch-id --stable | cut -d' ' -f1
    done)
fi

thence_patches=$(for hash in "${naive_list[@]}"; do
    git show --patch-with-raw "$hash" | git patch-id --stable
done)

thence_patches_uniq=$(echo "$thence_patches" | tac | awk -F' ' '{ map[$1]++ } (map[$1] == 1){ print }' | tac)

if [[ -n "${DEBUG+x}" ]]; then
    >&2 echo "---"
    >&2 echo "last_commit_time"
    >&2 echo "$last_commit_time"
    >&2 echo "naive_list"
    >&2 echo "${naive_list[@]}"
    >&2 echo "since_list"
    >&2 echo "${since_list[@]}"
    >&2 echo "thence_patches"
    >&2 echo "$thence_patches"
    >&2 echo "thence_patches_uniq"
    >&2 echo "$thence_patches_uniq"
    >&2 echo "---"
fi

# shellcheck disable=SC2207
diff_list=( $(echo "$thence_patches_uniq" | grep -F "$since_patches" -v | cut -d' ' -f2) )
if [[ ${#diff_list[@]} -eq 0 ]]; then
    exit 0;
fi

for hash in "${diff_list[@]}"; do
    git show -s --format="%h %s" "$hash"
done