Offer a quick way to the root nav even from a deep history stack

[gnprice]

When you're viewing one message feed, then follow a link (or recipient header) to another, and repeat several times, we keep each of those narrows on a history stack: if you navigate "back", we show you the previous messages you were just looking at.

That's important so that if you're reading conversation A and see a link someone posted to more context in conversation B, you can easily follow the link to see the context and then easily get back to conversation A to resume reading there.

But then a thing we don't currently offer is a way to quickly escape the whole history stack and get back to the navigation root, in order to look at something else. It'd be good to add such a way.

Instead, in the current app, you have to just go "back" N times if you're N pages deep in a chain of links. (That, or quit the app and reopen it.)

Discussion

The UX design question for this is somewhat tricky, because the most common UI patterns other apps have for getting quickly back to the root involve taking over the meaning of "back" (both the system gesture or button for it, and any "back" button inside the app like at the top left of the screen) so that it takes you up in the hierarchy, rather than back in your actual history. That breaks the ability to follow a link from conversation A to context in conversation B and easily return, as discussed above.

Patterns for this do exist, though — in particular it's fundamental to a web browser. @terpimost discussed some other examples in chat here.

This issue requires design discussion in chat before it will be ripe to work on.

[gnprice]

This is something we don't have in the legacy zulip-mobile app; the current approach is the way it's worked there for a number of years. It can be annoying, but I think isn't among the top problems with the app — there are other things we hear feedback about a lot more often. So placing this in the M7 Future milestone.