mergecopies: add logic to process incomplete data We first combine incomplete copies on the two sides of the topological CA into complete copies. Any leftover incomplete copies are then combined with the incomplete divergences to reconstruct divergences spanning over the topological CA. Finally we promote any divergences falsely flagged as incomplete to full divergences. Right now, there is nothing generating incomplete copy/divergence data, so this code does nothing. Changes to _checkcopies to populate these dicts are coming later in this series.

checkcopies: handle divergences contained entirely in tca::ctx During a graftlike merge, _checkcopies runs from ctx to tca, possibly passing over the merge base. If there is a rename both before and after the base, then we're actually dealing with divergent renames. If there is no rename on the other side of tca, then the divergence is contained entirely in the range of one _checkcopies invocation, and should be detected "in the loop" without having to rely on the other _checkcopies pass.

update: enable copy tracing for backwards and non-linear updates As a followup to the issue4028 series, this fixes a variant of the issue that can occur when updating with uncommited local changes. The duplicated .hgsub warning is coming from wc.dirty(). We would previously skip this call because it's only relevant when we're going to perform copy tracing, which we didn't do before. The change to the update summary line is because we now treat the rename as a proper rename (which counts as a change), rather than an add+delete pair (which counts as a change and a delete).