largefiles: call readstandin() with changectx itself instead of rev or node readstandin() takes "node" argument to get changectx by "repo[node]". There are some readstandin() invocations, which use ctx.node(), ctx.rev(), or '.' as "node" argument above, even though corresponded changectx object is already looked up on caller side. This patch calls readstandin() with already known changectx itself, to avoid meaningless re-construction of changectx (indirect case via copytostore() is also included). BTW, copytostore() uses "rev" argument only for readstandin() invocation. Therefore, this patch also renames it to "revorctx" to indicate that it can take not only revision ID or so but also changectx, for readability.