bisect: use && to connect statements that are deferred with eval.

Christian Couder pointed out that the existing eval strategy
swallows an initial non-zero return. Using && to connect
the statements should fix this.

Signed-off-by: Jon Seymour <jon.seymour@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-bisect.sh

@@ -86,7 +86,7 @@ bisect_start() {
 		0) state='bad' ; bad_seen=1 ;;
 		*) state='good' ;;
 		esac
-		eval="$eval bisect_write '$state' '$rev' 'nolog'; "
+		eval="$eval bisect_write '$state' '$rev' 'nolog' &&"
 		shift
 		;;
 	    esac
@@ -145,7 +145,7 @@ bisect_start() {
 	#
 	echo "$start_head" >"$GIT_DIR/BISECT_START" &&
 	git rev-parse --sq-quote "$@" >"$GIT_DIR/BISECT_NAMES" &&
-	eval "$eval" &&
+	eval "$eval true" &&
 	echo "git bisect start$orig_args" >>"$GIT_DIR/BISECT_LOG" || exit
 	#
 	# Check if we can proceed to the next bisect state.