merge: deprecate accessing update results by index Now that we have named attributes, let's convert the code base to use them. We also add deprecation warnings so legacy consumers are aware of their transgressions. ``stats.unresolvedcount`` is much easier to read than ``stats[3]``, don't you think? Differential Revision: https://phab.mercurial-scm.org/D2694

procutil: introduce context-manager interface for protect/restorestdio The code looks slightly cleaner since it was pretty easy to pass arguments in wrong order.