add sync script for updating the code

Add script for syncing contents with the kernel.
Compared to YNL C we only need to copy over the specs and deps.
YNL CPP has the generator (unlike YNL C which generates in
the kernel tree and copies over the outputs).

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

update-from-kernel.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+
+if [ $# -ne 1 ]; then
+    echo "Usage: $0 PATH_TO_KERNEL"
+    exit 1
+fi
+if [ $(dirname $0) != "." ]; then
+    echo "Script must be run directly in the ynl-c directory"
+    exit 1
+fi
+
+KSRC=$1
+
+cp -v ${KSRC}/tools/net/ynl/Makefile.deps	./
+sed -i 's@^UAPI_PATH:=.*@UAPI_PATH:=../@' Makefile.deps
+
+mkdir -p include/linux/
+for hdr in $(cat Makefile.deps | sed -n 's/.*,\([^,]*\.h\))/\1/p'); do
+    cp -v  ${KSRC}/include/uapi/linux/$hdr	./linux/
+done
+
+cp -rv ${KSRC}/Documentation/netlink Documentation/