Implementation plan: Submodule diff visibility

Branch: t3/repo-bug-fixes-3 | Date: 2026-10-14 | Spec: spec.md

Summary and technical context

Rust 2021 server, existing Git subprocesses, JSONL IPC and isolated TestServer fixtures. Pin --ignore-submodules=untracked in each explicit numstat/patch comparison: HEAD workspace, recorded-base task, turn trees and both selected-file paths. No new dependency or abstraction. Retain short gitlink patches and existing limits.

Constitution check

Spec clarified before implementation. Reproduce first using the existing real-IPC seam and local repositories; retain that fixture as the regression. Core/GUI/state remain untouched. No load-bearing architecture decision changes: this restores existing explicit comparison contracts from ADR-0016 and ADR-0029. Full proof and independent Standards/Spec reviews precede publishing. No exception needed.

Design and ownership

• git.rs owns HEAD workspace and task numstat calls.
• turns.rs owns tree-to-tree numstat comparisons and private snapshot capture. After ordinary add, enumerate stage records with mode 160000 and force-add only those literal NUL-delimited paths in the private index. This compensates for Git 2.55 skipping ignore=all links even during add --all; ignored ordinary files remain excluded. Existing TempIndex cleanup also removes the path file.
• file_diff.rs owns HEAD/base and tree-to-tree patches.
• tests/file_diff.rs exercises existing IPC and Git boundaries with local submodules.
• docs/08-ipc.md clarifies that Git ignore settings cannot hide gitlink changes.

Verification strategy

One local submodule advances a commit after a baseline. Assert exact removed/added Subproject commit lines, summary membership, HEAD/turn/task agreement and stable user index/config. Vary diff.ignoreSubmodules, local submodule ignore and .gitmodules ignore independently. Stage final source, run full and assess delivery proof.