Function prepare_interactive_selection 

pub fn prepare_interactive_selection(
    context: &GitContext,
    cwd: &Path,
    commit_index: &Path,
    object_directory: &Path,
    patch: bool,
    selection: &IndexSelection<'_>,
) -> Result<(), GitFailure>

What: Runs git add --patch or git add --interactive against the private index with inherited stdio. Why: The user’s terminal answers the selection, and the choice lands only in the private copy.

In TS you’d write (pseudocode):

await prepareInteractiveSelection({ workspace, gitPath, cwd, patch, pathspecs, pathspecFile, pathspecFileNul });