copies: move comment about implementation of mergecopies() to end When you start reading about mergecopies(), you want to know what it is, not that there are different implementations depending on config, so this patch moves that comment to the end. By the way, we don't seem to define what "copytracing" is. I'm just leaving it that way because I don't know what it is myself. It seems to be referred to only on mergecopies() (and not in pathcopies(), for example), so maybe "copytracing" is supposed to be exactly what mergecopies() does? Differential Revision: https://phab.mercurial-scm.org/D6235