standalone module for dump_placeholders?

[neogeographica]

When the completions script needs to do dump_placeholders, it currently has to load up the whole chaintool application. A lot of that isn't needed for dump_placeholders though. It would be possible to have a standalone module that only loads the core cmd and seq stuff to do the requested dump.

Not sure it would be noticeably faster, but maybe worth trying at some point.

[neogeographica]

Let's do it!