A bunch of the search options are globals in the module, so the behavior in terms of what gets used will be awfuly inconsistent:

* Case-sensitive & regexp settings will be ignored (since this API always passes in its own regexp)
* It will use whatever exclusion filter was in place the last time a search was run, since it's initialized in the Enter-key handler
* It will use whatever subtree scope was in place the last time the search bar was open (even if it was canceled, _unlike_ previous bullet), since that's initialized in `_doFindInFiles()`

Actually, looking at what else `_doFindInFiles()` does, it appears that this function would break pretty badly if an existing set of search results was still visible in the bottom panel.

Overall it seems like to expose this in a reliable way we'd need to rework how state is stored in this module to be more compartmentalized.  Doable, and a worthwhile cleanup anyway, but it requires much further-reaching code changes...