fix(terraform_docs): apply some of yermulnik suggestions

Author: tarfu

hooks/terraform_docs.sh

@@ -1,5 +1,6 @@
 #!/usr/bin/env bash
 set -eo pipefail
+
 # globals variables
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd -P)"
 readonly SCRIPT_DIR
@@ -237,10 +238,8 @@ function terraform_docs {
  have_marker=$(grep -o "$insertion_marker_begin" "$output_file") || unset have_marker
  [[ ! $have_marker ]] && popd > /dev/null && continue
  fi
- local config_options=""
- if [[ $have_config_flag == true ]]; then
- config_options="--config=$config_file"
- fi
+ local config_options
+ [[ $have_config_flag == true ]] && config_options="--config=$config_file"
  # shellcheck disable=SC2086
  terraform-docs --output-mode="$output_mode" --output-file="$output_file" $tf_docs_formatter "$config_options" $args ./ > /dev/null