Add a method to retrieve active material from MeshInstance

[clayjohn]

Closes: #31558 (comment)

Adds a new method to MeshInstance. get_active_material() returns the material that will be used to draw the mesh in order of overrides.

This should help fix the confusion users have when trying to retrieve the active material. Users often set the material in the mesh and then attempt to retrieve the MeshInstance surface material override and get null.

[akien-mga]

Needs a rebase after the 3D nodes renaming.

[clayjohn]

Ah, of course. And now we see the dangers of making a "simple" PR from your master branch.

[akien-mga]

Well it's the same as any branch in the end, updating it shouldn't impact your other branches/PRs in any way (only future branches if you base them off master, but I assume you've been using upstream/master for your PRs since then).

[clayjohn]

I've avoided touching my upstream master for many months. But my local master is another thing. It'll take a little got wrangling, but I should be able to get this under control. I'll do a little searching around and see if I can just move this over to another branch.

[akien-mga]

Note: By upstream I meant godotengine/godot.

You can't move the PR to another branch, you'd have to close it and create a new one.

But you can update your remote master branch easily from any local branch:

git remote clayjohn https://github.com/clayjohn/godot
git remote upstream https://github.com/godotengine/godot
git checkout clayjohn-master-fixed
git reset --hard clayjohn/master
git rebase -i upstream/master
// solve merge conflicts
git push --force clayjohn clayjohn-master-fixed:master

The key is the last command, git push's fully specified syntax is git push <remote> <local branch>:<remote branch> (so the local and remote branches can have different names).

[clayjohn]

@akien-mga Should be good now.

Your magic worked wonders, but for some reason it wasn't picking up on the last couple commits so the docs changes weren't captured. Had to do a manual, git pull --rebase to fix that up.

[akien-mga]

Right, upstream/master actually points to your local reference of the remote branch, so you need to git fetch upstream or git pull (which does a fetch) to update that reference and get the actaul godotengine/godot master HEAD. That's Git's intuitive interface for you :P

[akien-mga]

Thanks!