bookmarks: don't allow pushing new head for existing mark with -B (issue4400)

commands: fix help for debugobsolete

largefiles: fix explicit commit of normal/largefile switch Commit of corresponding normal/largefiles pairs would only commit the standin. That is usually fine, except if either the normal file or the standin is a remove while the other is an add. In that case it would either give duplicate colliding entries or lose the file. Instead, commit both filenames if one of them is a remove.