init_env: add a post-merge githook to remind user of re-init init_env
Created by: qais-yousef
post-merge githook will run after every git pull, and of course after any merge. Remind the developer that init_env must be re-sourced afresh to conitnue to get reliable lisa behavior.
Signed-off-by: Qais Yousef qais.yousef@arm.com