util.url: add an 'islocal' method This returns True if the URL represents a path that can be opened locally, without needing to go through the entire URL open mechanism.

push: move bookmarks exchange in the exchange module The bookmark exchange code was already extracted during a previous cycle. This changesets moves the extracted function in this module. This function will read and write data in the `pushoperation` object and It is preferable to have all core function collaborating through this object in the same place. This changeset is pure code movement only. Code change for direct consumption of the `pushoperation` object will come later.

push: move `newbranch` argument into the push object One more step toward a more modular push function.

push: move `revs` argument into the push object One more step toward a more modular push function.