A common situation: a developer builds an entire site, based on WordPress, of course, for a client.
This site includes many custom plugins as well as a custom theme -- maybe another theme or a child theme or two for good measure.
Doesn't make a lot of sense for all those custom plugins and such to have their own text domain. A single translator will probably doing all the work. It's also probably much easier to maintain a single set of translations.
So, how does one use a single text domain across multiple plugins and/or themes?
Just so we're clear, I want the equivalent of
load_theme_textdomain that I can use for multiple plugins/themes.