py3: use dict.update() instead of constructing lists and adding them dict.items() returned a list on Python 2 and whereas on Python 3 it returns a view object. So we required a work around. Using dict.update() is better then constructing lists as it should save us on gc churns.

patchbomb: add -B option to select a bookmark Add the -B/--bookmark option to select a bookmark whose changesets and its ancestors will be selected unless a new bookmark/head is found. This is inspired by hg strip -B option.