Function prune_excluded_refs 

async fn prune_excluded_refs(
    dest: &Path,
    default_branch: &str,
    include: &GlobSet,
    exclude: &GlobSet,
) -> Result<()>

Delete every branch/tag in the bare clone at dest that doesn’t pass git_ui.include/git_ui.exclude (see ref_is_included), then run git gc --prune=now so the excluded history isn’t merely unlisted but actually removed from what dumb HTTP ends up serving from disk.

A no-op (skips even the ref scan) when both include and exclude are empty, which is the common case.