pull: use `other.url()` as the source of a bookmark pull

We want to move the bookmarks movement into `exchange.pull`, for this purpose we
need to stop relying on variables from `command.pull`.

mercurial/commands.py

@@ -4961,7 +4961,7 b' def pull(ui, repo, source="default", **o'
                 raise util.Abort(err)
 
         modheads = repo.pull(other, heads=revs, force=opts.get('force'))
-        bookmarks.updatefromremote(ui, repo, remotebookmarks, source)
+        bookmarks.updatefromremote(ui, repo, remotebookmarks, other.url())
         # update specified bookmarks
         if opts.get('bookmark'):
             marks = repo._bookmarks