Merge branch 'sb/bisect-run-empty'

"git bisect run" that did not specify any command to run used to go
ahead and treated all commits to be tested as 'good'.  This has
been corrected by making the command error out.

* sb/bisect-run-empty:
  bisect run: die if no command is given

git-bisect.sh

@@ -450,6 +450,8 @@ bisect_replay () {
 bisect_run () {
 	bisect_next_check fail
 
+	test -n "$*" || die "$(gettext "bisect run failed: no command provided.")"
+
 	while true
 	do
 		command="$@"