Merge from vscode merge-base (#22780)

* Revert "Revert "Merge from vscode merge-base (#22769)" (#22779)"

This reverts commit 47a1745180.

* Fix notebook download task

* Remove done call from extensions-ci

extensions/git/src/uri.ts

@@ -51,3 +51,14 @@ export function toGitUri(uri: Uri, ref: string, options: GitUriOptions = {}): Ur
 		query: JSON.stringify(params)
 	});
 }
+
+/**
+ * Assuming `uri` is being merged it creates uris for `base`, `ours`, and `theirs`
+ */
+export function toMergeUris(uri: Uri): { base: Uri; ours: Uri; theirs: Uri } {
+	return {
+		base: toGitUri(uri, ':1'),
+		ours: toGitUri(uri, ':2'),
+		theirs: toGitUri(uri, ':3'),
+	};
+}