Display scene file extensions in the editor only if there's ambiguity

This also simplifies the Editor Settings as the extension is now
automatically shown to avoid ambiguity.

(cherry picked from commit 218d1247555417a203845c35160d5cc8af72e1d2)

editor/editor_data.cpp

@@ -790,18 +790,34 @@ Ref<Script> EditorData::get_scene_root_script(int p_idx) const {
 	return s;
 }
 
-String EditorData::get_scene_title(int p_idx) const {
+String EditorData::get_scene_title(int p_idx, bool p_always_strip_extension) const {
 	ERR_FAIL_INDEX_V(p_idx, edited_scene.size(), String());
 	if (!edited_scene[p_idx].root)
 		return TTR("[empty]");
 	if (edited_scene[p_idx].root->get_filename() == "")
 		return TTR("[unsaved]");
-	bool show_ext = EDITOR_DEF("interface/scene_tabs/show_extension", false);
-	String name = edited_scene[p_idx].root->get_filename().get_file();
-	if (!show_ext) {
-		name = name.get_basename();
+
+	const String filename = edited_scene[p_idx].root->get_filename().get_file();
+	const String basename = filename.get_basename();
+
+	if (p_always_strip_extension) {
+		return basename;
+	}
+
+	// Return the filename including the extension if there's ambiguity (e.g. both `foo.tscn` and `foo.scn` are being edited).
+	for (int i = 0; i < edited_scene.size(); i++) {
+		if (i == p_idx) {
+			// Don't compare the edited scene against itself.
+			continue;
+		}
+
+		if (edited_scene[i].root && basename == edited_scene[i].root->get_filename().get_file().get_basename()) {
+			return filename;
+		}
 	}
-	return name;
+
+	// Else, return just the basename as there's no ambiguity.
+	return basename;
 }
 
 void EditorData::set_scene_path(int p_idx, const String &p_path) {

editor/editor_data.h

@@ -193,7 +193,7 @@ public:
 	Node *get_edited_scene_root(int p_idx = -1);
 	int get_edited_scene_count() const;
 	Vector<EditedScene> get_edited_scenes() const;
-	String get_scene_title(int p_idx) const;
+	String get_scene_title(int p_idx, bool p_always_strip_extension = false) const;
 	String get_scene_path(int p_idx) const;
 	String get_scene_type(int p_idx) const;
 	void set_scene_path(int p_idx, const String &p_path);

editor/editor_settings.cpp

@@ -398,7 +398,6 @@ void EditorSettings::_load_defaults(Ref<ConfigFile> p_extra_config) {
 	hints["interface/theme/custom_theme"] = PropertyInfo(Variant::STRING, "interface/theme/custom_theme", PROPERTY_HINT_GLOBAL_FILE, "*.res,*.tres,*.theme", PROPERTY_USAGE_DEFAULT);
 
 	// Scene tabs
-	_initial_set("interface/scene_tabs/show_extension", false);
 	_initial_set("interface/scene_tabs/show_thumbnail_on_hover", true);
 	_initial_set("interface/scene_tabs/resize_if_many_tabs", true);
 	_initial_set("interface/scene_tabs/minimum_width", 50);

editor/rename_dialog.cpp

@@ -449,7 +449,10 @@ String RenameDialog::_substitute(const String &subject, const Node *node, int co
 	}
 
 	int current = EditorNode::get_singleton()->get_editor_data().get_edited_scene();
-	result = result.replace("${SCENE}", EditorNode::get_singleton()->get_editor_data().get_scene_title(current));
+	// Always request the scene title with the extension stripped.
+	// Otherwise, the result could vary depending on whether a scene with the same name
+	// (but different extension) is currently open.
+	result = result.replace("${SCENE}", EditorNode::get_singleton()->get_editor_data().get_scene_title(current, true));
 
 	Node *root_node = SceneTree::get_singleton()->get_edited_scene_root();
 	if (root_node) {