Add a script for backporting commits

Signed-off-by: Changyuan Lyu <changyuanl@google.com>

backport.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+set -e
+
+mkdir -p p9cpu
+for file in $(ls -A); do
+    if [ $file != "p9cpu" ] && [ $file != ".git" ] && [ $file != "backport.sh" ]; then
+        mv $file p9cpu/
+    fi
+done
+git add p9cpu
+git commit -m "tmp commit 1"
+git am $1
+HASH=$(git rev-parse HEAD)
+for file in $(ls -A p9cpu); do 
+    mv p9cpu/$file .
+done
+rm -r p9cpu
+git reset --soft HEAD~2
+git add .
+git commit -m "$(git log -1 --format=%B $HASH)"