upstream_merge:Add script to merge latest upstream

[chaitu236]

Add a script upstream_merge.sh that can be used to automate upstream merges. Also add a conf file for nilrt repos.

Testing

Ran script on OE sources

On a test repo with merge conflicts

On a test repo with no merge conflicts

[amstewart]

Looking at the docs for git submodule update --merge, it seems like a lot of what you're doing here might already be built into the git tooling. Have you considered using that command, and some of the git-submodule options that allow you to control how the update occurs (and maybe a composed .gitmodules file) to accomplish this same thing?

[chaitu236]

Looking at the docs for git submodule update --merge, it seems like a lot of what you're doing here might already be built into the git tooling. Have you considered using that command, and some of the git-submodule options that allow you to control how the update occurs (and maybe a composed .gitmodules file) to accomplish this same thing?

I wanted this script to be generic enough to be used for a single repo that isn't a submodule of another repo. So that we could extend it in future to work for linux.git (which currently doesn't work because the script doesn't support merging from tags).