Delete all git tags (remote and local) older than a given date [Linux/MacOS]

git-del-tag.sh

#!/bin/sh

# Make sure date is given
if [ $# -eq 0 ]
then
	printf "Usage:\n bash git-del-tag.sh 2018-04-23"
	exit 1
fi

# date command has different syntax for Linux and Mac
uname=$(uname)
case "$uname" in
	(*Linux*) dateCmd='date +%s -d' ;;
	(*Darwin*) dateCmd='date -j -f "%Y-%m-%d" +%s' ;;
esac

delRemoteCmd='git push --delete origin'
delLocalCmd='git fetch --prune origin "+refs/tags/*:refs/tags/*"'

# User given date to epoch timestamp
userTS=`eval "$dateCmd $1"`


git for-each-ref --sort=taggerdate --format 'tag=%(refname:short); date=%(taggerdate:short)' refs/tags |
{
	# Array of matching tags
	tags=()

	echo "Finding matching tags..."
	while read entry
	do
		eval "$entry"
		tagTS=`eval "$dateCmd $date"`
		
		if [ $userTS -ge $tagTS ];
		then
			tags[${#tags[*]}]="$tag"
		fi
	done
	
	# If no tags has been found just exit!
	if [ ${#tags[@]} -eq 0 ]
	then
		echo "No matching tags found. Quitting!"
		exit 0
	fi

	echo "Found ${tags[@]} tags..."
	echo "Following tags will be removed"
	echo "${tags[@]}"
	read -p "Are you sure you want to continue? [N/y]" docontinue < /dev/tty
	if [ "$docontinue" = "y" ];
	then
		echo "Removing remote tags..."
		eval "$delRemoteCmd ${tags[@]}"
		echo "Purging local tags..."
		eval "$delLocalCmd"
	fi
}

exit 0