log-tree: the previous one is still not quite right

The correct output would have NUL after each commit, so "-z --format=%s"
would have a single-liner subject with the line-terminating LF replaced
with NUL, and "-p/--stat -z --format=%s" would have a single-liner subject
with its line-terminating LF, followed by the diff/diffstat in which the
terminating LF of the last line is replaced with NUL, but to be consistent
with what "-p/--stat -z --pretty=format:%s" does, I think it is OK to
append NUL to the diff/diffstat part instead of replacing its last LF with
NUL.

The added test shows the update is still not right for "-p -z --format".

Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t4205-log-pretty-formats.sh

@@ -83,4 +83,20 @@ test_expect_success 'NUL termination' '
 	test_cmp expected actual
 '
 
+test_expect_success 'NUL separation with --stat' '
+	stat0_part=$(git diff --stat HEAD^ HEAD) &&
+	stat1_part=$(git diff --stat --root HEAD^) &&
+	printf "add bar\n$stat0_part\n\0initial\n$stat1_part\n" >expected &&
+	git log -z --stat --pretty="format:%s" >actual &&
+	test_cmp expected actual
+'
+
+test_expect_failure 'NUL termination with --stat' '
+	stat0_part=$(git diff --stat HEAD^ HEAD) &&
+	stat1_part=$(git diff --stat --root HEAD^) &&
+	printf "add bar\n$stat0_part\n\0initial\n$stat1_part\n\0" >expected &&
+	git log -z --stat --pretty="tformat:%s" >actual &&
+	test_cmp expected actual
+'
+
 test_done