Function first_commit_touching 

pub fn first_commit_touching(
    context: &GitContext,
    cwd: &Path,
    base: Option<&str>,
    current: &str,
    paths: &[String],
) -> Result<String, ReplayMergeError>

What: The first commit after the preparation base, in the landed history, that touches one of the paths; the current target when none does. Why: A conflict names the commit it lost to, so the integrator can show what changed under the prepared commit.

In TS you’d write (pseudocode):

await firstCommitTouching({ gitPath, cwd, base, current, paths });