Add prettier yml example hook

pre-commit.d/prettier-yml.py

@@ -0,0 +1,39 @@
+#!/usr/bin/env python
+
+import os
+import subprocess
+import sys
+
+from shutil import which
+
+file_extensions = (".yml", ".yaml",)
+prettier = os.getenv("PRETTIER_BIN", "./node_modules/.bin/prettier")
+options = ["--write"]
+
+if not which(prettier):
+    sys.exit("Prettier binary not found")
+
+diff = subprocess.check_output(
+    ["git", "diff", "--cached", "--name-only", "--diff-filter", "ACM"],
+    universal_newlines=True
+)
+
+yaml_files = [
+    item for item in diff.splitlines() if item.endswith(file_extensions)
+]
+
+if not yaml_files:
+    sys.exit(0)
+
+try:
+    output = subprocess.check_output(
+        [prettier, *options, *yaml_files],
+        universal_newlines=True,
+        stderr=subprocess.STDOUT
+    )
+except subprocess.CalledProcessError as e:
+    print("Formatting was unsuccessful:")
+    sys.exit(e.stdout)
+
+subprocess.run(["git", "add", "-u", *yaml_files])
+sys.exit(0)