chore: add legacy-migrations-version pre-commit hook

.pre-commit-config.yaml

@@ -89,6 +89,14 @@ repos:
         language: script
         files: ^installer/config.yml$
 
+      - id: legacy-migrations-version
+        name: legacy-migrations-version
+        description: Ensure valid schema version for migrations
+        entry: tools/legacy-migrations-version.sh
+        pass_filenames: false
+        language: script
+        files: ^api/libretime_api/legacy/migrations
+
       - id: legacy-assets-checksum-update
         name: legacy-assets-checksum-update
         description: Update legacy assets checksum

tools/legacy-migrations-version.sh

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+
+set -u
+
+error() {
+  echo >&2 "error: $*"
+  exit 1
+}
+
+migrations="api/libretime_api/legacy/migrations"
+version_file="$migrations/__init__.py"
+
+latest_migration="$(find "$migrations" -name '[0-9][0-9][0-9][0-9]_*.py' | sort | tail -n 1)"
+
+latest_migration_version="$(basename "$latest_migration" | cut -d '_' -f 1)"
+latest_migration_version="$((10#$latest_migration_version))" # Strip leading zeros
+
+sed \
+  -i "s#^LEGACY_SCHEMA_VERSION =.*#LEGACY_SCHEMA_VERSION = \"$latest_migration_version\"#" \
+  "$version_file"