narrow: drop server support for widening using the getbundle command (BC) The client still supports widening using the getbundle, which we (Google) still depend on a for a little while more (we've started the migration to the new narrow_widen command, but we're not done yet). Differential Revision: https://phab.mercurial-scm.org/D7093

widening: duplicate generateellipsesbundle2() for widening The widening and the non-widening code are quite different. It will be clearer to have them as sepearate functions. To start with, I've just copied it exactly, so it's clearer over the next few patches how they're different. The new function should gradually become more similar to bundle2.widen_bundle(), and should perhaps eventually be merged with that function. However, I've left it in narrowbundle2.py for now since it still depends on constants like _KILLNODESIGNAL there. Differential Revision: https://phab.mercurial-scm.org/D7092