Add argparse guard to potentially destructive script.

tools/dash-separated-format.py

@@ -1,9 +1,15 @@
 #!/usr/bin/python3
 import pathlib
 import subprocess
+import argparse
+
+parser = argparse.ArgumentParser()
+parser.add_argument('--run', action='store_true', help='whether to actually run potentially destructive commands')
+args = parser.parse_args()
 
 for filename in pathlib.Path('.').glob('**/*.md'):
     new_filename = str(filename).lower().replace(' ', '-')
     command = ['git', 'mv', str(filename), new_filename]
     print('would run: %s' % command)
-    # subprocess.run(command)
+    if args.run:
+        subprocess.run(command)