Improve reg_extension_icon docstring, add separate --extension.

reg_extension_icon.py

@@ -1,26 +1,48 @@
 '''
-I create my own icon files for some file types. This script edits the windows
-registry to assign the file extension icon and optionally a human-friendly name
-string. Must run as administrator.
+reg_extension_icon
+==================
+
+This script edits the windows registry HKEY_CLASSES_ROOT to assign a file
+extension icon and optionally a human-friendly name string.
+
+Must run as administrator.
 
 WARNING, if the extension is already associated with a program, or is otherwise
 connected to a progid, this will break it.
+
+> reg_extension_icon ico_file <flags>
+
+ico_file:
+    Filepath of the icon file.
+
+--extension:
+    If you omit this option, your file should be named "png.ico" or "py.ico" to
+    set the icon for png and py types. If the name of your ico file is not the
+    name of the extension you want to control, specify the extension here.
+
+--name:
+    A human-friendly name string which will show on Explorer under the "Type"
+    column and in the properties dialog.
 '''
 import argparse
 import sys
 import winreg
 
+from voussoirkit import betterhelp
 from voussoirkit import interactive
 from voussoirkit import pathclass
 
-def extension_registry(ico_file, human_name=None):
+def extension_registry(ico_file, extension=None, human_name=None):
     if ico_file.extension != 'ico':
         raise ValueError('Must provide a .ico file.')
 
-    name = ico_file.replace_extension('').basename
+    if extension is None:
+        extension = ico_file.replace_extension('').basename
+    else:
+        extension = extension.strip('.')
 
-    dot_ex = f'.{name}'
-    hash_ex = f'#{name}'
+    dot_ex = f'.{extension}'
+    hash_ex = f'#{extension}'
 
     prompt = [
         f'Set {dot_ex} = {hash_ex}',
@@ -47,10 +69,10 @@ def extension_registry(ico_file, human_name=None):
 
     print('Finished.')
 
-
 def extension_registry_argparse(args):
     return extension_registry(
         ico_file=pathclass.Path(args.ico_file),
+        extension=args.extension,
         human_name=args.name,
     )
 
@@ -58,11 +80,11 @@ def main(argv):
     parser = argparse.ArgumentParser(description=__doc__)
 
     parser.add_argument('ico_file')
+    parser.add_argument('--extension', default=None)
     parser.add_argument('--name', default=None)
     parser.set_defaults(func=extension_registry_argparse)
 
-    args = parser.parse_args(argv)
-    return args.func(args)
+    return betterhelp.single_main(argv, parser, __doc__)
 
 if __name__ == '__main__':
     raise SystemExit(main(sys.argv[1:]))