Tasks: Consolidate git merge-base/diff idiom

Mission: merge-base-diff-ssot-01KX44SD | Branch: fix/merge-base-diff-ssot | Spec: spec.md | Plan: plan.md

Behaviour-preserving consolidation of the 5-copy git merge-base → git diff --name-only idiom onto one core/vcs/git.py surface. Zero behaviour change (NFR-001).

Subtask Index

IDDescriptionWPParallel
T001Add git_merge_base primitiveWP01
T002Add git_diff_names primitive (pathspec + diff_filter, C-002 kwargs)WP01
T003Add merge_base_changed_files convenienceWP01
T004Direct tests: normal/empty-mb/mb-fail/diff-fail/pathspec/diff_filterWP01
T005Direct tests: non-HEAD branch-target (F1) + range↔two-arg equivalenceWP01
T006Repoint tasks_move_task._mt_pre_review_changed_filesWP02[P]
T007Repoint tasks_dependency_graph (two-ref primitive, NOT HEAD convenience)WP02[P]
T008Verify WP02 sites: no expected-value edits; dependency_graph branch-target assertedWP02
T009Repoint lanes/stale_check primitives (+C-002; update dead-symbol/arch guard)WP03[P]
T010Repoint tasks_shared first pass (preserve filter+dedup+content re-check verbatim)WP03[P]
T011Repoint acceptance._changed_workflow_files (5th copy; diff_filter=AMR; three-dot pin)WP03[P]
T012Verify WP03 sites + grep-verify zero residual copies across all 5 sites (SC-001)WP03
T013Add ScopeResult.from_override classmethodWP04
T014Retire hand-built ScopeResult in tasks_move_task override tier (out-of-map, respects symbol guard)WP04
T015Tests for from_override; confirm _MOVE_SET symbol-identity guard greenWP04

Work Packages

WP01 — Canonical merge-base/diff surface + direct tests

  • Goal: Create the single source of truth (git_merge_base, git_diff_names, merge_base_changed_files) in core/vcs/git.py, proven by direct tests. Foundation for all repoints.
  • Priority: P0 (MVP — everything depends on it) · Dependencies: none
  • Independent test: pytest -k merge_base_diff_surface green; all FR-006 branches (incl. F1 branch-target + range↔two-arg equivalence) exercised.
  • Requirements: FR-001, FR-006, NFR-002, NFR-003, NFR-004, C-002
  • Prompt: tasks/WP01-canonical-surface.md (~5 subtasks, ~300 lines)
  • ✅ T001 Add git_merge_base(repo, ref_a, ref_b) -> str | None (WP01)
  • ✅ T002 Add git_diff_names(repo, base, head, *, pathspec=None, diff_filter=None) -> tuple[str, ...] (WP01)
  • ✅ T003 Add merge_base_changed_files(worktree, base_ref, *, pathspec=None, diff_filter=None) -> tuple[str, ...] (WP01)
  • ✅ T004 Direct tests: normal, empty merge-base, merge-base fail, diff fail, pathspec, diff_filter (WP01)
  • ✅ T005 Direct tests: non-HEAD branch-target (F1 fence) + range↔two-arg equivalence on a real temp repo (WP01)

WP02 — Low-risk HEAD/branch repoints

  • Goal: Route the two straightforward copies through the surface, behaviour-preserving.
  • Priority: P1 · Dependencies: WP01 · Parallel with: WP03 (disjoint files)
  • Independent test: existing tasks_move_task + tasks_dependency_graph test suites green with no expected-value edits; a test asserts dependency_graph diffs check_branch, not HEAD.
  • Requirements: FR-002, FR-004, NFR-001, C-001
  • Prompt: tasks/WP02-low-risk-repoints.md (~3 subtasks, ~250 lines)
  • ✅ T006 Repoint tasks_move_task._mt_pre_review_changed_files → merge_base_changed_files (WP02)
  • ✅ T007 Repoint tasks_dependency_graph → git_merge_base(HEAD, check_branch) + git_diff_names(mb, check_branch) — two-ref, NOT convenience (WP02)
  • ✅ T008 Verify: no expected-value test edits (NFR-001); dependency_graph branch-target behaviour asserted (WP02)

WP03 — Higher-touch repoints

  • Goal: Route the three copies with extra behaviour to preserve, each with named acceptance criteria; verify the consolidation is complete.
  • Priority: P1 · Dependencies: WP01 · Parallel with: WP02 (disjoint files)
  • Independent test: stale_check, tasks_shared (lane-hygiene content-diff), and acceptance workflow-evidence suites green; grep shows zero residual merge-base/diff copies across all 5 sites.
  • Requirements: FR-003, FR-005, FR-008, NFR-001, NFR-002, C-001, C-002, C-003
  • Prompt: tasks/WP03-higher-touch-repoints.md (~4 subtasks, ~380 lines)
  • ✅ T009 Repoint lanes/stale_check primitives (+C-002 kwargs; update dead-symbol/arch guard for removed _git_merge_base/_git_diff_names) (WP03)
  • ✅ T010 Repoint tasks_shared._list_wp_branch_mission_specs_changes first pass; preserve startswith+dedup+content re-check verbatim (WP03)
  • ✅ T011 Repoint acceptance._changed_workflow_files (5th copy) → merge_base_changed_files(pathspec=".github/workflows", diff_filter="AMR"); pin three-dot↔two-arg equivalence (WP03)
  • ✅ T012 Verify all three sites + grep-verify zero residual copies (SC-001); full tests/architectural/ sweep + terminology guard + ruff/mypy (WP03)

WP04 — Secondary: ScopeResult.from_override tidy (deferrable)

  • Goal: Retire the hand-built ScopeResult construction behind a from_override classmethod. Isolated because of the _MOVE_SET symbol-identity guard (F7).
  • Priority: P3 (deferrable — may become a follow-up) · Dependencies: WP01, WP02 (WP02 lands the tasks_move_task diff first)
  • Independent test: from_override unit test green; test_tasks_move_task_seam.py module_defs == _MOVE_SET guard still green.
  • Requirements: FR-007
  • Prompt: tasks/WP04-scoperesult-from-override.md (~3 subtasks, ~200 lines)
  • □ T013 Add ScopeResult.from_override(targets) classmethod on review/pre_review_gate.py (WP04)
  • □ T014 Retire hand-built ScopeResult in tasks_move_task FR-004 override tier (out-of-map edit; no new module-level symbols) (WP04)
  • □ T015 Tests for from_override; confirm _MOVE_SET symbol-identity guard green (WP04)

Dependency Graph

WP01 (surface + tests)
 ├──> WP02 (low-risk repoints) ──> WP04 (secondary, deferrable)
 └──> WP03 (higher-touch repoints)     [WP02 ∥ WP03]

MVP & Parallelization

  • MVP: WP01 + WP02 + WP03 (the consolidation). WP04 is deferrable.
  • Parallel: WP02 ∥ WP03 once WP01 lands (disjoint owned_files).
  • Closeout gate (in WP03 T012): grep-verify zero residual copies; full tests/architectural/ sweep; terminology guard; ruff + mypy clean.