There are plenty of SO answers and tutorials on the web that say there is a difference between which branch is ours and which branch is theirs depending on whether it's a rebase or a merge, and explain why, usually with a handy table, as do the man pages and online docs (sans the table).
Thing is, I don't care to remember. I'm not a fan of cognitive load for trivial things that the computer should be able to tell me or simply show me.
Is there a command or ENV var or suchlike that contains this information? (A search of my env brings up nothing but maybe I need to enable something first). The kind of thing I can stick in the prompt would be perfect. If it can handle the middle of rebase with a conflict where the target branch becomes a reference to the commit reached, that would be even better.
As I explained here:
whatever HEAD's pointing to is "ours"
The one tool that makes crystal clear what is ours vs theirs is VSCode. See "Resolve merge conflicts"