src/vs/workbench/common/editor/resourceEditorInput.ts/AbstractResourceEditorInput/capabilities
class AbstractResourceEditorInput:	override get capabilities(): EditorInputCapabilities {
		let capabilities = EditorInputCapabilities.CanSplitInGroup;

		if (this.fileService.hasProvider(this.resource)) {
			if (this.fileService.hasCapability(this.resource, FileSystemProviderCapabilities.Readonly)) {
				capabilities |= EditorInputCapabilities.Readonly;
			}
		} else {
			capabilities |= EditorInputCapabilities.Untitled;
		}

		if (!(capabilities & EditorInputCapabilities.Readonly)) {
			capabilities |= EditorInputCapabilities.CanDropIntoEditor;
		}

		return capabilities;
	}