Vendoring bats libraries.

Signed-off-by: Chad Metcalf <chad@docker.com>

lib/bats-support/test/50-output-12-batslib_is_single_line.bats

@@ -0,0 +1,13 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+@test 'batslib_is_single_line() <string...>: returns 0 if all <string...> are single-line' {
+  run batslib_is_single_line 'a' $'b\n' 'c'
+  [ "$status" -eq 0 ]
+}
+
+@test 'batslib_is_single_line() <string...>: returns 1 if at least one of <string...> is longer than one line' {
+  run batslib_is_single_line 'a' $'b\nb' 'c'
+  [ "$status" -eq 1 ]
+}