Recover branch selection

[overengineer]

When user refreshes the stream, branch selection resets. As a workaround, I stored selected branch in a class member. Then used that value to get active branch. Better solutions are possible of course.

[JR-Morgan]

I haven't had a deep look at your PR just yet @overengineer
I'll make this a priority for next week.

Not sure if it relates to this PR. But I just thought I'd share my thoughts regardless.

In other connectors, we have tried to use the account id / stream id / branch id / commit id as the key for the selection instead of a sequential index.

I haven't investigated how possible this is, but we do look to be setting a Key here with str(i) (and similar elsewhere for accounts, commits, etc.)

This concept could also fix #98

[overengineer]

Hi @JR-Morgan
I updated my changes. Now I am matching objects by IDs.
Also I am checking if user and stream changed before restoring branch and commit selections.

I used hooks to listen user actions. because I could not find a way to access selection states.
BTW, I had to use those class members because all scene objects were resetting on update user.

I would prefer putting the code for selection states to a seperate file. But I hesitated because I do not know your folder structure conventions. If you have a suggestion, I can refactor.

[JR-Morgan]

Looking good, just a few comments

[overengineer]

@JR-Morgan
I made some changes according to your comments.

Also I converted class members to object members and instantiated the class. This way is less ugly I think.

[JR-Morgan]

Thanks @overengineer for your patience,
I've made a couple tiny tweaks to the type hinting, and merged.

Thanks for you contribution!

[JR-Morgan]

Change is now in 2.20.0-wip