#!/bin/sh -e
# git-cron-digest URL [BRANCH] - generate a digest of new commits since last run
#
# Example usage (daily fetch at 13:00):
# 0 13 * * *   : foo/bar ; git-cron-digest https://github.com/foo/bar

DATE=$(date "+%Y-%m-%d %H:%M:%S")

: ${GIT_CRON_DIGEST_DIR:=/var/tmp/git-cron-digest}

repo=$1
branch=$2
repohash=$(printf '%s\0' "$repo" "$branch" | git hash-object --stdin)
mkdir -p "$GIT_CRON_DIGEST_DIR"
if ! [ -d "$GIT_CRON_DIGEST_DIR/$repohash" ]; then
	cd "$GIT_CRON_DIGEST_DIR"
	git clone --mirror "$repo" ${2:+--branch=$branch} "$repohash"
	git -C "$repohash" config --add core.logAllRefUpdates true
	git -C "$repohash" update-ref -m "digest: initial clone" HEAD HEAD
fi
cd "$GIT_CRON_DIGEST_DIR/$repohash"
git update-ref -m "digest: pre-$DATE" HEAD HEAD
git fetch -q
if git log -1 --pretty=%h HEAD@{1}.. | grep -q .; then
	echo "New commits since $(git show -s --date=short-local --pretty=%cd HEAD@{1}):"
	echo
	git log --reverse --date=format-local:"%Y-%m-%d %H:%M" \
		--pretty="%cd %h %aE: %s" HEAD@{1}..
	echo
	git diff --shortstat --dirstat=cumulative,5 HEAD@{1}..
	printf '\n-- \ngit-cron-digest 0.1\n'
fi