Improve support for .htaccess when installing or converting to Multisite

[johnbillion]

When a site is converted to Multisite with wp core multisite-convert, or when Multisite is installed with wp core multisite-install, the relevant Multisite constants are added to wp-config.php, but nothing is added to .htaccess if the server is running on Apache.

Similarly, both of these commands provide an informational message saying "Don't forget to set up rewrite rules", but nothing about .htaccess is mentioned.

WP-CLI could either attempt to write to .htaccess itself, using the same rules that core generates after installing Multisite from the Tools -> Network Setup screen, or it could simply add an extra informational message about .htaccess.

[johnbillion]

I guess a link to the Nginx page on the Codex would help too, when Nginx is in use.

[danielbachhuber]

WP-CLI could either attempt to write to .htaccess itself, using the same rules that core generates after installing Multisite from the Tools -> Network Setup screen, or it could simply add an extra informational message about .htaccess.

The latter seems most appropriate to me, if WordPress' behavior is to display the rules but not attempt to add them.