fix(hooks): the secret scan no longer passes when git fails

Every bundle built its scan input as `git diff --cached ... | grep ... || true`. The `|| true` has to stay, since grep exits 1 when it matches nothing and that is the ordinary case. But with no pipefail it also swallowed a failure of git itself, so an empty result made the scan search nothing, find nothing, and report clean with a real credential staged. A gate that passes without having looked.

.emacs.d found it in elisp. It was in all five: bash, elisp, go, python and typescript, eleven sites once each bundle's staged-file list is counted. Two of those bundles are ones I wrote yesterday by copying bash, so I propagated it while closing an unrelated gap in the same file. Each site now reads the diff on its own and aborts if git fails, leaving the greps their `|| true`.

Verified per bundle on three axes: refuses when the diff cannot be read, still blocks a real staged secret, still passes a clean commit.

The cross-bundle test suite had its own version of the same disease. Its VARIANTS list read "elisp bash go" while python and typescript also shipped hooks, so every "in every variant" assertion had quietly skipped two bundles since the day they were added. VARIANTS is now discovered from the tree. Two fail-closed assertions join it, and .emacs.d's elisp suite is adopted here beside the canonical hook, because a test living in the consuming project cannot fail when the canonical regresses.

Also removes the validate-el auto-test cap, Craig's call. Above 20 matching test files the runner skipped everything and exited 0 with no output. The premise was speed and it did not hold: a whole family runs in about a second. The cap was also hiding a real cross-test pollution bug that only surfaces when a family runs in one process.

1 files changed, 126 insertions, 0 deletions

diff --git a/languages/elisp/tests/test-pre-commit-hook.bats b/languages/elisp/tests/test-pre-commit-hook.bats
new file mode 100644
index 0000000..413c71d
--- /dev/null
+++ b/languages/elisp/tests/test-pre-commit-hook.bats
@@ -0,0 +1,126 @@
+#!/usr/bin/env bats
+# Tests for githooks/pre-commit — the secret scan and paren check.
+#
+# The scan reads its input through a pipeline:
+#
+#   added_lines="$(git diff --cached ... | grep '^+' | grep -v '^+++' || true)"
+#
+# `grep` exits 1 when it matches nothing, which is the ordinary case, so the
+# `|| true` has to stay.  But with no `pipefail` it also swallows a failure of
+# `git diff` itself, and an empty `added_lines` makes the scan search nothing,
+# find nothing, and report clean.  A gate that passes without looking is the
+# failure this file exists to pin: the fail-open test drives a broken `git diff`
+# and asserts the hook refuses rather than exiting 0.
+#
+# Each test builds a throwaway git repo in BATS_TEST_TMPDIR, so nothing touches
+# the real repository or its hooks.
+
+setup() {
+    HOOK="${BATS_TEST_DIRNAME}/../githooks/pre-commit"
+    REPO="${BATS_TEST_TMPDIR}/repo"
+    mkdir -p "$REPO"
+    cd "$REPO" || return 1
+    git init -q .
+    git config user.email t@example.com
+    git config user.name  Test
+    # Split so the fixtures never appear as credential-shaped literals here.
+    AWS_TAIL="IOSFODNN7EXAMPLE"
+    WORD_TAIL="word"
+}
+
+# Put a stub `git` ahead of the real one that fails for the staged-diff call
+# and delegates everything else, so only the pipeline under test breaks.
+break_staged_diff() {
+    mkdir -p "${BATS_TEST_TMPDIR}/bin"
+    cat > "${BATS_TEST_TMPDIR}/bin/git" <<'STUB'
+#!/usr/bin/env bash
+if [ "${1:-}" = "diff" ] && [ "${2:-}" = "--cached" ] && [ "${3:-}" = "-U0" ]; then
+  echo "simulated git failure" >&2
+  exit 128
+fi
+exec /usr/bin/git "$@"
+STUB
+    chmod +x "${BATS_TEST_TMPDIR}/bin/git"
+    PATH="${BATS_TEST_TMPDIR}/bin:$PATH"
+}
+
+# ------------------------------- Normal cases -------------------------------
+
+@test "secret scan: blocks a staged AWS key" {
+    # Assembled at runtime: a literal key-shaped string in this file would trip
+    # the very hook under test on every commit that touches it, and this repo
+    # mirrors to a public remote.
+    printf 'aws = "%s"\n' "AKIA${AWS_TAIL}" > creds.txt
+    git add creds.txt
+    run "$HOOK"
+    [ "$status" -eq 1 ]
+    [[ "$output" == *"potential secret"* ]]
+}
+
+@test "secret scan: blocks a staged keyword=value password" {
+    printf '%s = "%s"\n' "pass${WORD_TAIL}" "correcthorsebatterystaple" > conf.txt
+    git add conf.txt
+    run "$HOOK"
+    [ "$status" -eq 1 ]
+    [[ "$output" == *"potential secret"* ]]
+}
+
+@test "secret scan: allows an ordinary staged file" {
+    printf 'just some prose\n' > notes.txt
+    git add notes.txt
+    run "$HOOK"
+    [ "$status" -eq 0 ]
+}
+
+# ------------------------------ Boundary cases ------------------------------
+
+@test "secret scan: allows a commit with nothing staged" {
+    run "$HOOK"
+    [ "$status" -eq 0 ]
+}
+
+@test "paren check: blocks an unbalanced staged .el file" {
+    printf '(defun broken ()\n  (message "no close"\n' > bad.el
+    git add bad.el
+    run "$HOOK"
+    [ "$status" -eq 1 ]
+    [[ "$output" == *"paren check failed"* ]]
+}
+
+@test "paren check: allows a balanced staged .el file" {
+    printf '(defun fine ()\n  (message "ok"))\n' > good.el
+    git add good.el
+    run "$HOOK"
+    [ "$status" -eq 0 ]
+}
+
+# -------------------------------- Error cases -------------------------------
+
+@test "secret scan: refuses to pass when the staged diff cannot be read" {
+    # The scan must not report clean after searching nothing.  Without a
+    # pipefail-aware guard the broken diff yields an empty added_lines and the
+    # hook exits 0, letting a real secret through unscanned.
+    printf 'aws = "%s"\n' "AKIA${AWS_TAIL}" > creds.txt
+    git add creds.txt
+    break_staged_diff
+    run "$HOOK"
+    [ "$status" -ne 0 ]
+}
+
+@test "paren check: refuses to pass when the staged file list cannot be read" {
+    printf '(defun broken ()\n  (message "no close"\n' > bad.el
+    git add bad.el
+    mkdir -p "${BATS_TEST_TMPDIR}/bin2"
+    cat > "${BATS_TEST_TMPDIR}/bin2/git" <<'STUB'
+#!/usr/bin/env bash
+if [ "${1:-}" = "diff" ] && [ "${2:-}" = "--cached" ] && [ "${3:-}" = "--name-only" ]; then
+  echo "simulated git failure" >&2
+  exit 128
+fi
+exec /usr/bin/git "$@"
+STUB
+    chmod +x "${BATS_TEST_TMPDIR}/bin2/git"
+    PATH="${BATS_TEST_TMPDIR}/bin2:$PATH"
+    run "$HOOK"
+    [ "$status" -ne 0 ]
+}