copy: move mergecopies file logic to a function Moves the mergecopies nonoverlap logic to a separate function so that other extensions which may need to prefetch information about the files being processed have a hook point. This saves extensions from having to recompute this information themselves, and thus saves several seconds off of various commands (like rebase).

histedit: allow configuring default behavior Adds a configuration setting for allowing users to specify the default behavior of 'hg histedit' without arguments. This saves users from having to manually figure out the bottom commit or a complicated revset. My current revset of choice is "only(.) & draft() - ::merge()" The commits that histedit can work with is usually quite limited, so if this feature ends up working well, we may want to consider making "only(.) & draft() - ::merge()" the default behavior for everyone.