abuild: checksum modifies the APKBUILD directly

abuild

@@ -94,7 +94,7 @@ md5check() {
 		return 0
 	fi
 	if [ -z "$md5sums" ]; then
-		die "Use 'abuild checksum >>$APKBUILD' to generate a checksum"
+		die "Use 'abuild checksum' to generate/update the checksum(s)"
 	fi
 
 	if [ "$(echo $source | wc -l)" -ne "$(echo $md5sums | wc -l)" ]; then
@@ -494,14 +494,17 @@ builddeps() {
 	done
 }
 
+# replace the md5sums in the APKBUILD
 checksum() {
 	local s files
 	fetch
+	msg "Updating the md5sums in APKBUILD..."
 	for s in $source; do
 		files="$files ${s##*/}"
 	done
 	md5sums="$(cd "$srcdir" && md5sum $files)" || die "md5sum failed"
-	echo "md5sums=\"$md5sums\""
+	sed -i -e '/^md5sums="/,/"\$/d; /^md5sums=''/,/''\$/d' "$APKBUILD"
+	echo "md5sums=\"$md5sums\"" >>"$APKBUILD"
 }
 
 stripbin() {