history merge in private mode clears history

[PatrickF1]

echo $version
3.5.0

Yes, I tested this without third-party customizations.

How to repro

1. Spawn a new fish session in private mode: sh -c 'env HOME=$(mktemp -d) fish --private'
2. Run a few commands; doesn't matter what you type because even invalid commands make it into history
3. Check history using history
4. history merge
5. Check history again and notice it is now blank

Is this a bug or intended?

[faho]

Yeah, sure, I just made it error out - merging history in private mode is by definition wrong.

[PatrickF1]

Thanks! But where does it say that it's by definition wrong? It seems to me it should actually just proceed with incorporating history into the current session.

[faho]

Merging goes both ways. And I really really really don't want to add a secondary path that barely anybody uses that needs us to only do half of that.

[PatrickF1]

I didn't know merging goes both ways. Yeah I agree erroring is the right choice here, thanks!