manifest-cache: ignore IOError while writing If the wcache directory is non writable for some reason (eg: belong to root). Trying to write to it currently crash Mercurial. Instead we ignore the error and skip writing that cache. We should probably improve the user experience of multiple users interacting with the same repository. However this is not an adventure for stable. Differential Revision: https://phab.mercurial-scm.org/D8512

copy: give better error message when no source paths found with --at-rev The new error message matches what we show when marking copies in the working copy. Differential Revision: https://phab.mercurial-scm.org/D8496

tests: show poor error message for `hg cp -A --at-rev . non-existent dst` Differential Revision: https://phab.mercurial-scm.org/D8495

copy: to find copy source, walk parent of revision we're marking copies in As shown in the previous patch, `hg cp --after --at-rev . src dst` fails if `src` is not in `.`. It seems obvious that you should always walk the *parent* of the revision you're marking copies in, but that's not how it was done for the working copy, and I didn't think to change it when marking copies in a non-working-copy commit. This patch fixes that by walking the parent commit instead, but only if we're marking copies for a non-working-copy commit. We need to leave the working-copy code unchanged because it depends on the weird behavior of `workingctx.walk()`. With these changes, there's very little overlap between the working-copy version and the non-working-copy version of `walkpats()`, but I've refrained from cleaning that up on the stable branch. Differential Revision: https://phab.mercurial-scm.org/D8494