Make RPM spec in contrib more aligned with the one from Fedora This is mostly syntactical changes which make the real differences more obvious when looking at a diff. contrib/mergetools.rc is now also installed and enabled by default.

addremove: drop some silly variable assignments

ui.prompt: Show prompt and selection in non-interactive mode ui.prompt was completely silent in non-interactive mode, unless in verbose mode. It is fine that it chooses the default automatically, but it is confusing that the message and prompt shown interactively can't be found in scripted tests. The prompt and selection is now .write'ed instead of .note'ed.