feat(folders): Add zen.folders.new-tabs-in-folder to open new tabs in current folder

[mehdi-sy-h]

Adds a new zen.folders.new-tabs-in-folder preference. When enabled, new tabs via Ctrl + T will open under the currently open tab's parent folder. This saves having to continually move new tabs into the desired folder.

Relevant discussion: #13669

[mr-cheffy]

We don't typically add patches like these, specially if they are just going to be hidden advanced preferences and without any tests. What would be the use case of this?

[mehdi-sy-h]

Sorry yes I can add some tests I was just wondering if this is a feature that might get merged. There's already the zen.folders.owned-tabs-in-folder pref which does something similar but for tabs that were middle clicked.

As for use case, generally when you're browsing/researching about a specific topic you might want to keep all those tabs under one folder, especially if you're someone who has a lot of tabs already and want things structured. Middle click is useful but not complete because you might read something for example and then search for that specific thing with Ctrl+T and have that tab be under the same folder. Without this feature there's a lot of friction in moving the relevant new tab(s) into the folder again and again and your tabs end up being cluttered again.

Imo this is a slightly separate use case than Spaces, because you might want the same containers, theme settings, etc but you still want grouping by subtopic within that space. Say you have a space for "Work" with its own container, and you're working on a bunch of different projects at work, so you group them by folder. Switching to different projects at a given time is rare, but searching for things related to the same topic is more common (you're reading docs, you see a concept you're not aware of, you open a new tab searching for it, etc).

[mr-cheffy]

Unsure how this would work with split views.

[mehdi-sy-h]

For split views should I see if all of the tabs are part of the same folder and then add them, otherwise not?

[mehdi-sy-h]

Actually it looks like trying to do a split view with a tab in a folder and a tab outside of a folder is buggy in upstream already. And for a split view of tabs across two different folders, it moves one tab into the other's folder?

[mehdi-sy-h]

What kind of tests would be useful? I imagine one similar to the existing owner tabs test test_Duplicate_Tab_Inside_Folder.