Grepped for callsites, browsed around in Pholio.
withMocks(...) now has the effect of working like a cache and implying withMockPHIDs(...), similar to withRepositories(...) elsewhere.
There's a behavioral change here: we'll now load Images if they have a null value for mockPHID (i.e., an image not yet attached to a mock). Previously, we would always reject them.
(Not actually that scary: it does some extra fetches, but hits the cache the second time through.)
This fixes a sort-of-bug. The mpull() intends to rekey the array (the lines below care about the array keys) but changes the values instead. The code worked before because the array happened to always be keyed by ID anyway.