copies: fix duplicatecopies() with overlay context The reasoning for this check is in 78d760aa3607 (duplicatecopies: do not mark items not in the dirstate as copies, 2013-03-28). The check was then moved to workingfilectx in 754b5117622f (context: add workingfilectx.markcopied, 2017-10-15) and no corresponding check was added later when overlayworkingfilectx was added. Rather than adding the check there, this patch adds a more generic check on the callers side and removes the check in workingfilectx.markcopied(). Differential Revision: https://phab.mercurial-scm.org/D6380

tests: demonstrate crash when rebasing across copy with --collapse As reported by timeless. Differential Revision: https://phab.mercurial-scm.org/D6379

exthelper: add some semi-useful trace logs It'd be nice to make the trace functions a little better-named in the output, but I'm not sure how much better we can do without overhead. This at least lets you see if a single reposetup function is eating all the time or if it's spread over all of them. I needed this because Google's uber-extension has a long load time and I wasn't sure where the problem was. Differential Revision: https://phab.mercurial-scm.org/D6381