Show all theme releases from the last month. The script should be placed in wp-content/themes/ and your themes should have .git/ in root.

show_releases_from_to.sh

#!/bin/bash
#
# Gist: https://gist.github.com/primozcigler/e816919feea345ca393dc4ae90a872fd
# How to use it: https://primoz.blog/simple-bash-script-can-tell-releases-given-date-period/

if [[ $# -ne 2 ]]; then
	echo "usage: $0 <start date> <end date>"
	echo "<date> in format 'YYYY-MM-DD'"
	exit
fi

for theme_path in $(find . -maxdepth 1 -mindepth 1 -type d); do
	cd $theme_path
	if [[ -d .git ]]; then
		git pull -q
		releases=$(git log --tags --after="$1" --before="$2" --simplify-by-decoration --pretty="format:%ci %d")
		if [[ $releases ]]; then
			echo "Releases for ${theme_path}:"
			echo "${releases}"
			echo
		fi
	fi
	cd ..
done