Look in config for sites-subdir

[neclimdul]

Fix #3495

Not sure if this is the "correct" fix but it fixes the problem.

[weitzman]

Would be ideal to get a review from @greg-1-anderson since he made #2982

[weitzman]

Please see if #3495 (comment) fixes this for you.

[greg-1-anderson]

This should be solved via configuration injection, as suggested in #3495 (comment).

If the issue is that only command-specific options are working here, and a global sites-subdir configuration option is not respected, we should investigate that and fix it in config injection. We don't want to add explicit calls to config->get() when it is possible to inject the value.

[neclimdul]

@greg-1-anderson that seems to be the case. Also, sites subdir resolution fails to fallback on default when a URI is provided. fix for that here #3591

[neclimdul]

I'm not sure how "If the issue is that only command-specific options are working here, and a global sites-subdir configuration option is not respected" should be addressed but I think the original issue has been addressed pretty thoroughly so closing this.