CI: Add workflow to verify test vectors are up-to-date

It will also help us to avoid unintentional modifications to existing
test vectors.

.github/workflows/test_vectors.yml

@@ -0,0 +1,36 @@
+name: Check test vectors
+
+on: pull_request
+
+jobs:
+  verify:
+    name: ${{ matrix.name }}
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        kind: ['rust', 'json', 'zcash']
+        include:
+          - kind: 'rust'
+            extension: 'rs'
+            name: 'Rust'
+          - kind: 'json'
+            extension: 'json'
+            name: 'JSON'
+          - kind: 'zcash'
+            extension: 'rs'
+            name: 'Bitcoin-flavoured JSON'
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Install poetry
+        run: pip install --user poetry
+
+      - name: Install dependencies
+        run: poetry install --no-root
+
+      - name: Regenerate test vectors
+        run: ./regenerate.sh ${{ matrix.kind }} ${{ matrix.extension }}
+
+      - name: Verify there are no changes
+        run: git diff -s --exit-code

regenerate.sh

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+
+tv_scripts=(
+    f4jumble_long
+    f4jumble
+    orchard_empty_roots
+    orchard_generators
+    orchard_group_hash
+    orchard_key_components
+    orchard_map_to_curve
+    orchard_merkle_tree
+    orchard_note_encryption
+    orchard_poseidon_hash
+    orchard_poseidon
+    orchard_sinsemilla
+    sapling_generators
+    sapling_key_components
+    sapling_note_encryption
+    sapling_signatures
+    sapling_zip32)
+
+for generator in "${tv_scripts[@]}"
+do
+    echo "# $generator"
+    poetry run python ./$generator.py -t $1 >test-vectors/$1/$generator.$2
+done