Use directories instead of individual files

This change updates the `packer_validate` hook to run against
directories instead of against each file. This will correctly allow
configurations to be split across multiple files but be treated as a
single configuration when the hook is run.

.pre-commit-hooks.yaml

@@ -6,6 +6,7 @@
   language: script
   files: \.pkr\.hcl$
   pass_filenames: true
+  require_serial: true
 
 - id: packer_fmt
   name: Packer Format

hooks/packer_validate.sh

@@ -25,13 +25,23 @@ while (("$#")); do
   esac
 done
 
+paths=()
+index=0
+for file in "${files[@]}"; do
+  paths[index]=$(dirname "$file")
+  ((++index))
+done
+
+unique_paths=()
+while IFS='' read -r line; do unique_paths+=("$line"); done < <(printf '%s\n' "${paths[@]}" | sort --unique)
+
 error=0
 
-for file in "${files[@]}"; do
-  if ! packer validate "${args[@]}" "$file"; then
+for path in "${unique_paths[@]}"; do
+  if ! packer validate "${args[@]}" "$path"; then
     error=1
     echo
-    echo "Failed path: $file"
+    echo "Failed path: $path"
     echo "================================"
   fi
 done