Add comment to the beginning of automatically generated env file

Author: peanutfun

requirements/env_climada.yml

@@ -1,3 +1,5 @@
+# DO NOT MODIFY!
+# This file was automatically generated by make_conda_env.py
 channels:
 - conda-forge
 - nodefaults

script/make_conda_env.py

@@ -5,6 +5,7 @@
 # dependencies = ["PyYAML"]
 # ///
 import tomllib
+from datetime import datetime
 from pathlib import Path
 from typing import Any
 
@@ -16,6 +17,11 @@
 DELETIONS = []
 
 
+def this_file_name() -> str:
+    """Return the name of this file"""
+    return Path(__file__).name
+
+
 def read_pyproject(path: str | Path = "pyproject.toml") -> dict[str, Any]:
     """Read the pyproject file as dict"""
     with open(path, "rb") as file:
@@ -72,8 +78,13 @@ def write_environment_file(
         "channels": ["conda-forge", "nodefaults"],
         "dependencies": sorted(dependencies),
     }
+    content = yaml.dump(data)
+    content = (
+        "# DO NOT MODIFY!\n"
+        f"# This file was automatically generated by {this_file_name()}\n"
+    ) + content
     with open(output_path, "w") as file:
-        yaml.dump(data, file)
+        file.writelines(content)
 
 
 def main():