fix(hooks): resolve the output dir from GRAPHIFY_OUT in the sh gates, not a literal graphify-out/

#1423 moved the Python rebuild bodies onto GRAPHIFY_OUT, but the shell that
runs BEFORE them still hardcoded graphify-out/. With the documented override
(#686, e.g. GRAPHIFY_OUT=custom-out for worktree/shared-output setups):

- post-checkout exited at `[ ! -d "graphify-out" ]`, so a branch switch never
  launched the rebuild - a silent no-op with nothing in the log.
- post-commit's "only graph artifacts changed" filter only recognised
  graphify-out/ paths, so a commit touching only custom-out/graph.json
  launched a full rebuild - the loop the filter exists to prevent.

Both gates now read ${GRAPHIFY_OUT:-graphify-out}, the same source the rebuild
body reads. The commit filter is a POSIX case loop instead of grep so the dir
name is matched literally (no regex metacharacters); the leading ( on each
pattern keeps bash 3.2 (macOS /bin/sh) from mis-parsing the pattern's ) inside
the $(...) substitution.

Regression: tests/test_hooks.py runs the emitted scripts under sh with the
launcher stubbed and asserts whether the hook reaches the launch line.

Claude-Session: https://claude.ai/code/session_0134ujLF81GyXsCByibLcYsz
(cherry picked from commit 9efd052de4)

graphify/hooks.py

@@ -415,8 +415,20 @@ if [ -z "$CHANGED" ]; then
     exit 0
 fi
 
-# Skip when only graphify-out/ artifacts changed (avoids rebuild loop when graph outputs are tracked in git)
-_NON_GRAPH=$(echo "$CHANGED" | grep -v '^graphify-out/' || true)
+# Skip when only output-dir artifacts changed (avoids rebuild loop when graph
+# outputs are tracked in git). The dir is whatever GRAPHIFY_OUT names, the same
+# source the rebuild body reads (#1423): a literal graphify-out/ here let a
+# commit touching only a renamed output dir's graph.json trigger a full rebuild.
+_GFY_OUT="${GRAPHIFY_OUT:-graphify-out}"
+_GFY_OUT="${_GFY_OUT%/}"
+# The leading ( on each pattern is POSIX and keeps bash 3.2 (macOS /bin/sh)
+# from mis-parsing the pattern's ) as the end of the $(...) substitution.
+_NON_GRAPH=$(printf '%s\n' "$CHANGED" | while IFS= read -r _GFY_F; do
+    case "$_GFY_F" in
+        ("$_GFY_OUT"/*) ;;
+        (*) printf '%s\n' "$_GFY_F" ;;
+    esac
+done)
 if [ -z "$_NON_GRAPH" ]; then
     exit 0
 fi
@@ -468,8 +480,11 @@ fi
 # branch switch but leaves the tree unchanged ΓÇö nothing to rebuild (#2421).
 [ "$PREV_HEAD" = "$NEW_HEAD" ] && exit 0
 
-# Only run if graphify-out/ exists (graph has been built before)
-if [ ! -d "graphify-out" ]; then
+# Only run if the output dir exists (graph has been built before). Resolve it
+# from GRAPHIFY_OUT like the rebuild body does (#1423): a literal graphify-out/
+# here made the branch-switch rebuild a silent no-op for every renamed output dir.
+_GFY_OUT="${GRAPHIFY_OUT:-graphify-out}"
+if [ ! -d "${_GFY_OUT%/}" ]; then
     exit 0
 fi
 

tests/test_hooks.py

@@ -1406,3 +1406,130 @@ def test_hook_probes_snap_confined_uv_tool_dirs():
 
     assert '"$HOME"/snap/*/[0-9]*/.local/share/uv/tools' in _HOOK_SCRIPT
     assert '"$HOME"/snap/*/current/.local/share/uv/tools' in _HOOK_SCRIPT
+
+
+# ── GRAPHIFY_OUT: the shell gates in front of the rebuild must honour it ─────
+#
+# #1423 moved the Python rebuild bodies onto GRAPHIFY_OUT, but the sh that runs
+# BEFORE them still hardcoded graphify-out/: post-checkout exited unless a
+# literal graphify-out/ directory existed, and post-commit's "only graph
+# artifacts changed" filter only recognised graphify-out/ paths. With the
+# documented override (#686) the branch-switch rebuild therefore never launched
+# and a commit touching only the renamed output dir triggered a full rebuild.
+# Behaviour of the emitted script under a real sh, per the #2126/#2641
+# convention, with the launcher stubbed so the test observes whether the hook
+# REACHES the launch rather than running a rebuild.
+
+_LAUNCH_LINE = "launching background rebuild"
+
+
+def _stub_python(tmp_path: Path) -> Path:
+    """A 'python' that passes the find_spec probe and swallows the launcher."""
+    py = tmp_path / "stubpy"
+    py.write_text("#!/bin/sh\nexit 0\n", encoding="utf-8", newline="\n")
+    py.chmod(0o755)
+    return py
+
+
+def _emitted_hook_run(repo: Path, script: str, args: list[str], env_extra: dict[str, str]):
+    stub = _stub_python(repo.parent)
+    rendered = script.replace("__PINNED_PYTHON__", str(stub)).replace("__VIZ_LIMIT_EXPORT__", "")
+    hook = repo.parent / "emitted-hook.sh"
+    hook.write_text(rendered, encoding="utf-8", newline="\n")
+    env = dict(os.environ)
+    env["HOME"] = str(repo.parent / "home")
+    for key in ("GIT_DIR", "GRAPHIFY_OUT", "GRAPHIFY_SKIP_HOOK"):
+        env.pop(key, None)
+    env.update(env_extra)
+    return subprocess.run(
+        ["sh", str(hook), *args], capture_output=True, text=True, cwd=str(repo), env=env,
+    )
+
+
+def _git(repo: Path, *args: str) -> None:
+    subprocess.run(
+        ["git", "-c", "user.name=t", "-c", "user.email=t@example.com",
+         "-c", "core.hooksPath=/dev/null", "-C", str(repo), *args],
+        check=True, capture_output=True,
+    )
+
+
+def _repo_with_graph_only_commit(tmp_path: Path, out_dir: str) -> Path:
+    """Two commits: a source file, then ONLY <out_dir>/graph.json — the
+    tracked-output case the post-commit filter exists for."""
+    repo = tmp_path / "repo"
+    repo.mkdir()
+    _git(repo, "init", "-q")
+    (repo / "a.py").write_text("x = 1\n", encoding="utf-8")
+    _git(repo, "add", "a.py")
+    _git(repo, "commit", "-q", "-m", "src")
+    (repo / out_dir).mkdir()
+    (repo / out_dir / "graph.json").write_text("{}", encoding="utf-8")
+    _git(repo, "add", f"{out_dir}/graph.json")
+    _git(repo, "commit", "-q", "-m", "graph")
+    return repo
+
+
+_SH_ONLY = pytest.mark.skipif(
+    shutil.which("sh") is None or os.name == "nt", reason="sh required to run the emitted hook"
+)
+
+
+@_SH_ONLY
+def test_checkout_hook_rebuilds_when_graphify_out_is_renamed(tmp_path):
+    repo = tmp_path / "repo"
+    repo.mkdir()
+    _git(repo, "init", "-q")
+    (repo / "custom-out").mkdir()  # the configured output dir; no graphify-out/
+    result = _emitted_hook_run(repo, _CHECKOUT_SCRIPT, ["aaa", "bbb", "1"], {"GRAPHIFY_OUT": "custom-out"})
+    assert result.returncode == 0, result.stderr
+    assert _LAUNCH_LINE in result.stdout, (
+        "post-checkout exited before the launch: it gates on a literal graphify-out/ "
+        f"instead of $GRAPHIFY_OUT\nstdout={result.stdout!r}\nstderr={result.stderr!r}"
+    )
+
+
+@_SH_ONLY
+def test_checkout_hook_still_skips_when_no_graph_was_built(tmp_path):
+    """Control: with neither the default nor the configured dir present there is
+    no graph to refresh, so the branch-switch hook stays a no-op."""
+    repo = tmp_path / "repo"
+    repo.mkdir()
+    _git(repo, "init", "-q")
+    result = _emitted_hook_run(repo, _CHECKOUT_SCRIPT, ["aaa", "bbb", "1"], {"GRAPHIFY_OUT": "custom-out"})
+    assert result.returncode == 0, result.stderr
+    assert _LAUNCH_LINE not in result.stdout
+
+
+@_SH_ONLY
+def test_commit_hook_skips_graph_only_commit_when_graphify_out_is_renamed(tmp_path):
+    repo = _repo_with_graph_only_commit(tmp_path, "custom-out")
+    result = _emitted_hook_run(repo, _HOOK_SCRIPT, [], {"GRAPHIFY_OUT": "custom-out"})
+    assert result.returncode == 0, result.stderr
+    assert _LAUNCH_LINE not in result.stdout, (
+        "post-commit launched a rebuild for a commit that only touched the configured "
+        f"output dir\nstdout={result.stdout!r}"
+    )
+
+
+@_SH_ONLY
+def test_commit_hook_skips_graph_only_commit_under_default_dir(tmp_path):
+    """Control: the default-name case the filter always handled keeps working."""
+    repo = _repo_with_graph_only_commit(tmp_path, "graphify-out")
+    result = _emitted_hook_run(repo, _HOOK_SCRIPT, [], {})
+    assert result.returncode == 0, result.stderr
+    assert _LAUNCH_LINE not in result.stdout
+
+
+@_SH_ONLY
+def test_commit_hook_still_rebuilds_for_a_source_change(tmp_path):
+    """Control: a commit that touches source alongside the renamed output dir
+    must still launch — the filter drops output-dir paths, not the rebuild."""
+    repo = _repo_with_graph_only_commit(tmp_path, "custom-out")
+    (repo / "b.py").write_text("y = 2\n", encoding="utf-8")
+    (repo / "custom-out" / "graph.json").write_text("{\"n\": 1}", encoding="utf-8")
+    _git(repo, "add", "b.py", "custom-out/graph.json")
+    _git(repo, "commit", "-q", "-m", "src+graph")
+    result = _emitted_hook_run(repo, _HOOK_SCRIPT, [], {"GRAPHIFY_OUT": "custom-out"})
+    assert result.returncode == 0, result.stderr
+    assert _LAUNCH_LINE in result.stdout, result.stdout