add auto update drone

.util.sh

@@ -0,0 +1,18 @@
+#!/bin/sh
+
+update_pkg() {
+
+  updpkgsums > /dev/null 2>&1
+
+  if [ $? -eq 0 ]
+  then
+      makepkg --printsrcinfo > .SRCINFO
+      git add .SRCINFO PKGBUILD
+      git commit -m "$(basename $(pwd)): update to $ver" > /dev/null 2>&1
+      if [ $? -eq 0 ]
+      then
+          git push
+      fi
+  fi
+
+}

drone/update.sh

@@ -0,0 +1,9 @@
+#!/bin/sh
+
+source ../.util.sh
+
+ver=`curl -s https://api.github.com/repos/drone/drone/tags | jq -r '.[0].name' | cut -c2-`
+echo $ver
+sed -i "s/pkgver=.*/pkgver=${ver}/" PKGBUILD
+
+update_pkg