Option format text should replace newlines with spaces

[warsaw]

In Mailman 3, we write options like so:

@click.option(
    '-C', '--config', 'config_file',
    envvar='MAILMAN_CONFIG_FILE',
    type=click.Path(exists=True, dir_okay=False, resolve_path=True),
    help=_("""\
    Configuration file to use.  If not given, the environment variable
    MAILMAN_CONFIG_FILE is consulted and used if set.  If neither are given, a
    default configuration file is loaded."""))

This makes it possible to translate the help text, but because the source formatting is a triple quoted string, there are embedded newlines in the help text. We have to preserve the original source string text so that it can be looked up in the i18n catalog, and we can't really change the _() function to strip newlines at runtime because the source strings are extracted by an offline process that does not execute the source code.

After some pdb tracing, I've noticed that click already dedents the help text, which is great, but it also needs to substitute spaces for newlines, otherwise the wrapping of the help text isn't correct. For example, the above by default gets printed on the console like so:

$ mailman --help
...
Options:
  -C, --config PATH  Configuration file to use.  If not given, the
                     environment variable
                     MAILMAN_CONFIG_FILE is consulted
                     and used if set.  If neither are given, a
                     default
                     configuration file is loaded.

Here's a small change that makes the -C option print correctly:

    def format_options(self, ctx, formatter):
        """Writes all the options into the formatter if they exist."""
        opts = []
        for param in self.get_params(ctx):
            rv = param.get_help_record(ctx)
            if rv is not None:
                part_a, part_b = rv
                opts.append((part_a, part_b.replace('\n', ' ')))

        if opts:
            with formatter.section('Options'):
                formatter.write_dl(opts)

and now:

$ mailman --help
...
Options:
  -C, --config PATH  Configuration file to use.  If not given, the
                     environment variable MAILMAN_CONFIG_FILE is consulted
                     and used if set.  If neither are given, a default
                     configuration file is loaded.

Much better!

[fdavis]

Thanks for the issue and all the details!
There have been a quite few issues regarding formatting. Notably #513.
Hopefully we can gather all of these bits up and define a good format interface