Add header to generated requirements

requirements-dev.txt

@@ -1,3 +1,4 @@
+# DO NOT EDIT THIS FILE DIRECTLY - use ./script/update-requirements to update
 Pygments==2.13.0
 attrs==22.1.0
 black==22.10.0

requirements.txt

@@ -1,3 +1,4 @@
+# DO NOT EDIT THIS FILE DIRECTLY - use ./script/update-requirements to update
 PyYAML==6.0
 dnspython==2.3.0
 fqdn==1.5.1

script/update-requirements

@@ -2,6 +2,7 @@
 
 from os.path import join
 from subprocess import check_call, check_output
+from sys import argv
 from tempfile import TemporaryDirectory
 import re
 
@@ -43,10 +44,14 @@ dev_frozen = sorted([p for p in dev_frozen
 print_packages(frozen, 'frozen')
 print_packages(dev_frozen, 'dev_frozen')
 
+script = argv[0]
+
 with open('requirements.txt', 'w') as fh:
+    fh.write(f'# DO NOT EDIT THIS FILE DIRECTLY - use {script} to update\n')
     fh.write('\n'.join(frozen))
     fh.write('\n')
 
 with open('requirements-dev.txt', 'w') as fh:
+    fh.write(f'# DO NOT EDIT THIS FILE DIRECTLY - use {script} to update\n')
     fh.write('\n'.join(dev_frozen))
     fh.write('\n')