rebase: check that the bookmark is still valid when restoring (issue4669) After a rebase --abort, we attempt to restore the previously active bookmark. We need to ensure that the bookmark still exists.

bookmarks: rename current to active in variables and comments Today, the terms 'active' and 'current' are interchangeably used throughout the codebase in reference to the active bookmark (the bookmark that will be updated with the next commit). This leads to confusion among developers and users. This patch is part of a series to standardize the usage to 'active' throughout the mercurial codebase and user interface.