test-lib.sh: do not "echo" caller-supplied strings

In some places we "echo" a string that is supplied by the calling
test script and may contain backslash sequences. The echo command
of some shells, most notably "dash", interprets these backslash
sequences (POSIX.1 allows this) which may scramble the test
output.
Signed-off-by: NUwe Storbeck <uwe@ibr.ch>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/test-lib.sh

@@ -277,7 +277,7 @@ error "Test script did not set test_description."
 
 if test "$help" = "t"
 then
-	echo "$test_description"
+	printf '%s\n' "$test_description"
 	exit 0
 fi
 
@@ -328,7 +328,7 @@ test_failure_ () {
 	test_failure=$(($test_failure + 1))
 	say_color error "not ok $test_count - $1"
 	shift
-	echo "$@" | sed -e 's/^/#	/'
+	printf '%s\n' "$*" | sed -e 's/^/#	/'
 	test "$immediate" = "" || { GIT_EXIT_OK=t; exit 1; }
 }