context: filter out invalid copies from workingctx.p[12]copies() workingctx normally gets its lists of modified, added, removed files etc. based on the dirstate status. Its constructor also accepts a "changes" argument to override the status from the dirstate. This is used for partial commits. If a "changed" argument was passed, we should clearly also filter out copies to those paths, which I had previously missed. This patch adds that filtering and fixes the bugs demonstrated in the previous patch. Differential Revision: https://phab.mercurial-scm.org/D6750