[Unit]
Description=Regenerate grub-btrfs.cfg

[Service]
Type=oneshot
#Inital setup
EnvironmentFile=/etc/grub.d/41_snapshots-btrfs_config
ExecStartPre=-/bin/bash -c '[ ! -f "/boot/${GRUB_BTRFS_DIRNAME:-grub}/grub-btrfs.cfg" ] && grub2-mkconfig -o /boot/${GRUB_BTRFS_DIRNAME:-grub}/grub.cfg'
#Regenerate grub-btrfs.cfg instead of the whole grub menu
ExecStart=/etc/grub.d/41_snapshots-btrfs