Merge branch 'pf/editor-ignore-sigint'

The behaviour visible to the end users was confusing, when they attempt to kill a process spawned in the editor that was in turn launched by Git with SIGINT (or SIGQUIT), as Git would catch that signal and die. We ignore these signals now. * pf/editor-ignore-sigint: launch_editor: propagate signals from editor to git run-command: do not warn about child death from terminal launch_editor: ignore terminal signals while editor has control launch_editor: refactor to use start/finish_command run-command: drop silent_exec_failure arg from wait_or_whine