Flash GSIs or even full ROMs as DSU (full ROM only works if it is compatible with currently installed ROM's kernel)

gsi_tool_flasher.sh

#!/bin/bash
set -e

function unsparse_if_needed() {
	if [ "$(file -b $1 | cut -f1 -d ',')" = "Android sparse image" ]; then
		echo "Unsparsing..."
		simg2img "$1" "$1".raw
		mv "$1".raw "$1"
	fi
}

function unpack_img_from_zip() {
	local ZIP="$1"
	local IMG="$2"
	local DST="$3"
	local DAT_BR="$IMG".new.dat.br
	local TRANSFER_LIST="$IMG".transfer.list
	if [ ! -z "$(zipinfo -1 $ZIP | grep $DAT_BR)" ]; then
		unzip -p "$ZIP" "$DAT_BR" > "$DST".dat.br
		unzip -p "$ZIP" "$TRANSFER_LIST" > "$DST".transfer.list
		rm -f "$DST".dat
		brotli -d "$DST".dat.br
		rm "$DST".dat.br
		rm -rf sdat2img
		git clone https://github.com/xpirt/sdat2img
		./sdat2img/sdat2img.py "$DST".transfer.list "$DST".dat "$DST"
		rm "$DST".dat "$DST".transfer.list
	else
		unzip -p "$ZIP" "$IMG".img > "$DST"
	fi
	unsparse_if_needed "$DST"
}

if [ -z "$1" ]; then
	echo "Usage: $0 <GSI>"
	exit 1
fi

REQUIREMENTS="adb brotli file git gunzip simg2img unzip unxz zipinfo"
for REQUIREMENT in $REQUIREMENTS; do
	if [ -z "$(command -v $REQUIREMENT)" ]; then
		echo "Command $REQUIREMENT is missing, please install it!"
		exit 1
	fi
done

IMG="$1"
EXT="$(echo $IMG | rev | cut -f1 -d '.' | rev)"

if [ "$EXT" = "xz" ]; then
	echo "unxz $IMG"
	unxz "$IMG"
	IMG="$(echo $IMG | rev | cut -f2- -d '.' | rev)"
elif [ "$EXT" = "gz" ]; then
	echo "gunzip $IMG"
	gunzip -k "$IMG"
	IMG="$(echo $IMG | rev | cut -f2- -d '.' | rev)"
elif [ "$EXT" = "zip" ]; then
	echo "Extracting system.img"
	NEWIMG="$(echo $IMG | rev | cut -f2- -d '.' | rev)"
	unpack_img_from_zip "$IMG" system "$NEWIMG"
	IMG="$NEWIMG"
else
	unsparse_if_needed "$IMG"
fi
IMGNAME="$(basename $IMG)"
adb wait-for-device root
adb wait-for-device push "$IMG" /sdcard/
adb wait-for-device shell "gsi_tool install --userdata-size 8589934592 --install-dir /data/gsi/dsu --gsi-size $(du -b $IMG) --no-reboot < /sdcard/$IMGNAME"
if [ "$EXT" = "zip" ]; then # can contain multiple images
	for PART in $(zipinfo -1 "$1"); do
		EXT="$(echo $PART | cut -f2- -d '.')"
		PART="$(echo $PART | cut -f1 -d '.')"
		[ "$EXT" != "img" ] && [ "$EXT" != "new.dat.br" ] && continue;
		if [ "$PART" = "system_ext" ] || [ "$PART" = "odm" ] || [ "$PART" = "product" ] || [ "$PART" = "vendor" ]; then
			if [ "$PART" = "vendor" ] || [ "$PART" = "odm" ]; then
				read -e -p "Really flash device-specific image $PART? (y/n): " -i "y" flash
				[ ! -z "$flash" ] && [ "$flash" != "y" ] && continue;
			fi
			echo "Installing additional image: $PART"
			unpack_img_from_zip "$1" "$PART" "$IMG"
			adb wait-for-device push "$IMG" /sdcard
			adb wait-for-device shell "gsi_tool create-partition --install-dir /data/gsi/dsu --partition-name $(echo $PART | cut -f1 -d '.') --size $(du -b $IMG) < /sdcard/$IMGNAME"
		fi
	done
fi
adb wait-for-device shell rm /sdcard/"$IMGNAME"
rm "$IMG"
rm -rf sdat2img
echo "You can now boot your new DSU installation, have fun!"