Create a cursory changelog from a git log

generate_changelog.sh

# Generates a cursory changelog from all tags in a git log
# All params are optional. If the from param is empty,
# it will create a changelog from all tags
#
# @param from - the tag or git commit to start from
# @param to - the tag or git commit to end at
# @param title - a title to give the log if specifying the previous options

function generate_changelog {
	local changes hash log log_title tag tags prev from="$1" to="$2" title nl=$'\n';

	if [[ -z "$from" ]]; then
		tags=$(git for-each-ref --format='%(*committerdate:raw)%(committerdate:raw) %(refname) %(*objectname) %(objectname)' refs/tags | sort -n | awk '{ gsub("refs/tags/", "", $3); print $3; }');
	else
		title="$3"
		tags="$from..$to"
	fi

	for tag in $tags; do
		[[ -n $prev ]] && hash="$prev..$tag" || hash="$tag";
		log_title="$title"
		if [[ -z "$log_title" ]]; then
			log_title=$(IFS=$'\n'; echo $(git log -n1 $tag --pretty=format:'%s - %cd' --date=short) | awk -F' - ' '{ "date -j -f \"%Y-%m-%d\" "$2" +\"%B %d, %Y\"" |getline d; print $1" - "d }');
		fi

		log=$(echo "## $log_title$nl"; g log --pretty=format:'* %s' "$hash" | grep -ivE 'Merge branch|Source Format|Rebuild|Build files' | /usr/bin/grep -vE '^\* \d+\.\d+\.\d+$'; echo "");

		changes="${nl}${log}${nl}$changes";
		prev="$tag";
	done;

	echo "$changes"
}