My script for migrating AUR3 to AUR4 (I keep a copy of all src and bin packages in a .backup subdirectory).

mkaur4

#!/bin/bash

if [ ! -d .git ] ; then
	if [ ! -f PKGBUILD ] ; then
		echo "ERROR: need PKGBUILD to do anything!" >&2
		exit 1
	fi
	echo "--> initializing git repository"
	git init
	echo "--> rebuilding .SRCINFO file"
	mksrcinfo
	if [ -f .SRCINFO ] ; then
		echo "--> adding .SRCINFO"
		git add .SRCINFO
	else
		echo "ERROR: no .SRCINFO generated" >&2
		exit 1
	fi
	pkgbase=$(cat .SRCINFO|grep '^pkgbase = '|awk '{print$3;}')
	if [ -z "$pkgbase" ] ; then
		echo "ERROR: no pkgbase" >&2
		exit 1
	else
		echo "--> pkgbase is $pkgbase"
	fi
	echo "--> adding PKGBUILD"
	git add PKGBUILD
	ifiles=$(cat .SRCINFO|grep '^[[:space:]]*install = '|awk '{print$3;}')
	echo "--> install files: $ifiles"
	cfiles=$(cat .SRCINFO|grep '^[[:space:]]*changelog = '|awk '{print$3;}')
	echo "--> changelog files: $cfiles"
	sfiles=$(cat .SRCINFO|grep '^[[:space:]]*source = '|awk '{print$3;}')
	echo "--> source files: $sfiles"
	for f in $ifiles $cfiles $sfiles; do
		echo "--> checking $f"
		if [ -f $f ] ; then
			echo "--> adding $f"
			git add $f
		else
			echo "WARNING: file $f does not exist"
		fi
	done
	echo "--> commiting initial version"
	git commit -m 'initial version'
	echo "--> adding aur4 as remote aur"
	git remote add --tags aur ssh+git://aur4.archlinux.org/${pkgbase}.git/
	if [ -d .backup ]; then
		echo "--> processing .backup directory"
		srcfiles=$(ls -rt .backup/${pkgbase}-*.src.tar.gz)
		for f in $srcfiles ; do
			if [ -f $f ] ; then
				echo "--> processing $f"
				echo "    --> untarring $f"
				tar --strip-components=1 -xvf $f
				echo "    --> making .SRCINFO for $f"
				mksrcinfo
				files=$(tar -tf $f|sed 's,.*/,,')
				echo "    --> adding .SRCINFO $files"
				git add .SRCINFO $files
				v=$(echo "$f"|sed "s,\.backup/$pkgbase-,,;s,\.src.tar.gz,,")
				d=$(stat -c '%y' "$f"|awk '{print$1" "$2;}'|sed 's,\..*$,,')
				echo "    --> commiting version $v"
				git commit -m "version $v" --date="$d"
			fi
		done
	fi
fi

Note: you also need to do the following after the script has run and the git repo looks the way that you want it:

$> git push -u aur master

That's all.