bookmarks: Set current bookmark if we create a new one on the tip
If track.current is enabled we set the newly created bookmark as the
current tracked bookmark. We do not do this if a revision is specified.
% no bookmarks
no bookmarks set
% set bookmark X
% list bookmarks
* X -1:000000000000
% update to bookmark X
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
% list bookmarks
* X -1:000000000000
% rename
% list bookmarks
* Z -1:000000000000
% new bookmark Y
% list bookmarks
* Y -1:000000000000
Z -1:000000000000
% commit
% list bookmarks
* Y 0:719295282060
Z -1:000000000000