resolve: fix incorrect merge The merge from stable into default was semantically incomplete -- a couple of changes in preceding code had to be rewritten here. This code only triggers for change/delete conflicts, so we can't test it yet. We will soon be able to do it, though.

fileset: add missing() predicate (issue4925) Help of status cmd defines status file of 'missing', what is called in fileset 'deleted'. To stay consistent this patch introduces missing() predicate which in fact is alias to 'deleted'.

webutil: make _siblings into an object with __iter__ and __len__ _siblings is a helper that is used for displaying changeset parents and children in hgweb. Before, when it was a simple generator, it couldn't tell its length without being consumed, and that required a special case when preparing data for changeset template (see 9e1f4c65f5f5). Let's make it into a class (similar to templatekw._hybrid) that allows len(...) without side-effects.

mergestate: move binary format documentation into _readrecordsv2 This is too low-level to be the top-level documentation for mergestate. We're restricting the top-level documentation to only be about what consumers of the mergestate and anyone extending it need to care about.

unshelve: add support for custom merge tools For parity with merge --tool, rebase --tool etc. rebase.rebase overwrites the tool in repo.ui, so we need to explicitly pass it down there too.

unshelve: shed spurious space