checkout: add --progress option Under normal circumstances, and like other git commands, git checkout will write progress info to stderr if attached to a terminal. This option allows progress to be forced even if not using a terminal. Also, progress can be skipped if using option --no-progress. Signed-off-by: Edmundo Carmona Antoranz <eantoranz@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>