argparse docs: prog default is the basename of argv[0] (GH-30298)

Author: lf-

Doc/library/argparse.rst

@@ -148,7 +148,8 @@ ArgumentParser objects
    as keyword arguments. Each parameter has its own more detailed description
    below, but in short they are:
 
-   * prog_ - The name of the program (default: ``sys.argv[0]``)
+   * prog_ - The name of the program (default:
+     ``os.path.basename(sys.argv[0])``)
 
    * usage_ - The string describing the program usage (default: generated from
      arguments added to parser)

Lib/argparse.py

@@ -1691,7 +1691,8 @@ class ArgumentParser(_AttributeHolder, _ActionsContainer):
     """Object for parsing command line strings into Python objects.
 
     Keyword Arguments:
-        - prog -- The name of the program (default: sys.argv[0])
+        - prog -- The name of the program (default:
+            ``os.path.basename(sys.argv[0])``)
         - usage -- A usage message (default: auto-generated from arguments)
         - description -- A description of what the program does
         - epilog -- Text following the argument descriptions