Function read_tree_discard 

pub fn read_tree_discard(region: &[OsString]) -> Discard

What: Read a git read-tree region. Why: --reset replaces the index and, with -u, the worktree, dropping every unmerged and local entry. --res is the shortest prefix that --recurse-submodules does not share.

In TS you’d write (pseudocode):

function readTreeDiscard(region: string[]): Discard;