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, 20 insertions, 3 deletions

diff --git a/languages/elisp/githooks/pre-commit b/languages/elisp/githooks/pre-commit
index 2c0cf0b..a87bedf 100755
--- a/languages/elisp/githooks/pre-commit
+++ b/languages/elisp/githooks/pre-commit
@@ -18,8 +18,18 @@ cd "$REPO_ROOT" || exit 1
 SECRET_PATTERNS_CS='(AKIA[0-9A-Z]{16}|sk-[a-zA-Z0-9_-]{20,}|-----BEGIN (RSA|DSA|EC|OPENSSH|PGP)( PRIVATE)?( KEY| KEY BLOCK)?-----)'
 SECRET_PATTERNS_CI='(api[_-]?key|api[_-]?secret|auth[_-]?token|secret[_-]?key|bearer[_-]?token|access[_-]?token|password)[[:space:]]*[:=][[:space:]]*["'"'"'][^"'"'"']{16,}["'"'"']'
 
-added_lines="$(git diff --cached -U0 --diff-filter=AM \
-  | grep '^+' | grep -v '^+++' || true)"
+# Read the diff on its own so a git failure is distinguishable from "grep
+# matched nothing". Both end in a non-zero status, but only one of them means
+# there is nothing to scan; piping them together and swallowing the result with
+# `|| true` made a broken git look like a clean commit — the scan searched an
+# empty string, found nothing, and the secret went in.
+if ! staged_diff="$(git diff --cached -U0 --diff-filter=AM)"; then
+  echo "pre-commit: cannot read the staged diff — refusing to skip the secret scan" >&2
+  exit 1
+fi
+
+# The greps keep their `|| true`: exiting 1 on no match is their normal result.
+added_lines="$(printf '%s\n' "$staged_diff" | grep '^+' | grep -v '^+++' || true)"
 
 cs_hits="$(printf '%s\n' "$added_lines" | grep -nE  "$SECRET_PATTERNS_CS" || true)"
 ci_hits="$(printf '%s\n' "$added_lines" | grep -niE "$SECRET_PATTERNS_CI" || true)"
@@ -37,7 +47,14 @@ if [ -n "$secret_hits" ]; then
 fi
 
 # --- 2. Paren check on staged .el files ---
-staged_el="$(git diff --cached --name-only --diff-filter=AM | grep '\.el$' || true)"
+# Same split as the secret scan above: a git failure must not read as "no files
+# staged", which would skip the language check silently.
+if ! staged_names="$(git diff --cached --name-only --diff-filter=AM)"; then
+  echo "pre-commit: cannot read the staged file list — refusing to skip the check" >&2
+  exit 1
+fi
+
+staged_el="$(printf '%s\n' "$staged_names" | grep '\.el$' || true)"
 
 if [ -n "$staged_el" ]; then
   paren_fail=""