Duplicate tracks on animation reimport - GLTF

[CowKeyMan]

Godot version: 3.2.2

OS/device including version: Windows

Issue description: On presssing reimportfor a .glb file, my animation tracks that I created in blender (not custom ones that I created in godot, those are fine) for every single animation that I have, get duplicted. This didnt happen in 3.2.1, because I tested it, and had to revert to that version because of this issue. This happens for both .tres as well as .anim.

Note: turning off 'keep custom tracks' will 'fix' this bug, however I need custom tracks for my game, hence this is not a valid solution for myself

Steps to reproduce: Please refer to this video: https://youtu.be/rvnMbUBGHAI (notice how the tracks for bone1-3 got duplicated for every reimport I did). I also attached an image of the errors that come with the bug

Minimal reproduction project: You can test it out using this project: AnimationImportingBugTest.zip

[Sl3dge78]

Ok this on is on me sorry, working on a fix...

Here's my reply on the pr i was cced #39968

Hey thank you for cc ing me and sorry if my PR caused any issues...

Just to understand your issue, you imported a scene with animation to external files, modified existing tracks and/or added new ones, and finally saved said animation. Then when pressing reimport what happened?

Here's what I just tested on my side and what happens in both cases :

* Import a .dae file with animation and store the animation outside the dae

* Edit an animation (by changing tracks or adding new ones) and save it

* Reimport the .dae with the Keep Custom Tracks enabled.

old behaviour (before my pr):

* Edited tracks are reverted

* Created tracks are kept

new behaviour (with my pr):

* It duplicates all tracks (that's a big issue!)

This is where the merge happens :

godot/editor/import/resource_importer_scene.cpp

Lines 959 to 971 in 73262c0

	if (FileAccess::exists(ext_name) && p_keep_animations) {
	//try to keep custom animation tracks
	Ref<Animation> old_anim = ResourceLoader::load(ext_name, "Animation", true);
	if (old_anim.is_valid()) {
	//meergeee
	for (int i = 0; i < old_anim->get_track_count(); i++) {
	if (!old_anim->track_is_imported(i)) {
	old_anim->copy_track(i, anim);
	}
	}
	anim->set_loop(old_anim->has_loop());
	}
	}

The snippet above adds any track that isn't marked as imported from the old file to the new file, so that's why.

Maybe the operation shouldn't be a copy but a replace? If the track exists, replace it if its not imported.
If the user wants to reverts the changes he has made he can untick "keep custom tracks"