VSCode extension API: simple local Quick Diff - version-control

Question

Trying to understand how to implement simple source control management in my language extension.
I need to show a Quick Diff for a single file (my extension doesn't work with folders) compared with some special one.
Let's say i have this TextDocumentContentProvider and QuickDiffProvider:
class MyLangDocumentContentProvider implements vscode.TextDocumentContentProvider
{
provideTextDocumentContent(uri: vscode.Uri)
{
return getFileText(uri); // returns text of provided file uri
}
}
class MyLangRepository implements vscode.QuickDiffProvider
{
provideOriginalResource(uri: vscode.Uri)
{
return getOriginalFileUri(uri); // returns uri of the special file to compare with
}
}
Then in activate method of extension i initialize them:
const docProvider = new MyLangDocumentContentProvider();
const gitSCM = vscode.scm.createSourceControl('git', 'Git');
gitSCM.quickDiffProvider = new MyLangRepository();
const workingTree = gitSCM.createResourceGroup('workingTree', 'Changes');
workingTree.resourceStates = [
{ resourceUri: vscode.window.activeTextEditor.document.uri }
];
Then i need to call registerTextDocumentContentProvider with some custom uri scheme. So why do i need custom uri scheme? And what else should i do to track changes of current file relative to the special one?
I was looking at vscode-extension-samples/source-control-sample, but it looks more complicated then my case.
Thanks for any advices!

Answer 1

Though my question was rather sily, let me save here some kind of instruction, how I've done this.
to make QuickDif work you don't need neither ResourceGroups nor TextDocumentContentProvider, this is a separate functionality.
SourceControl (and also its quickDiffProvider) will work if you pass some root directory in constructor (I've got no luck without thoug I don't need it for my purpose).