[PATCH v3 3/9] config tests: add "NULL" tests for *_get_value_multi()

[Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>]

A less well known edge case in the config format is that keys can be
value-less, a shorthand syntax for "true" boolean keys. I.e. these two
are equivalent as far as "--type=bool" is concerned:

	[a]key
	[a]key = true

But as far as our parser is concerned the values for these two are
NULL, and "true". I.e. for a sequence like:

	[a]key=x
	[a]key
	[a]key=y

We get a "struct string_list" with "string" members with ".string"
values of:

	{ "x", NULL, "y" }

This behavior goes back to the initial implementation of
git_config_bool() in 17712991a59 (Add ".git/config" file parser,
2005-10-10).

When the "t/t1308-config-set.sh" tests were added in [1] only one of
the three "(NULL)" lines in "t/helper/test-config.c" had any test
coverage. This change adds tests that stress the remaining two.

1. 4c715ebb96a (test-config: add tests for the config_set API,
   2014-07-28)

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
---
 t/t1308-config-set.sh | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/t/t1308-config-set.sh b/t/t1308-config-set.sh
index b38e158d3b2..561e82f1808 100755
--- a/t/t1308-config-set.sh
+++ b/t/t1308-config-set.sh
@@ -146,6 +146,36 @@ test_expect_success 'find multiple values' '
 	check_config get_value_multi case.baz sam bat hask
 '
 
+test_expect_success 'emit multi values from configset with NULL entry' '
+	test_when_finished "rm -f my.config" &&
+	cat >my.config <<-\EOF &&
+	[a]key=x
+	[a]key
+	[a]key=y
+	EOF
+	cat >expect <<-\EOF &&
+	x
+	(NULL)
+	y
+	EOF
+	test-tool config configset_get_value_multi a.key my.config >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'multi values from configset with a last NULL entry' '
+	test_when_finished "rm -f my.config" &&
+	cat >my.config <<-\EOF &&
+	[a]key=x
+	[a]key=y
+	[a]key
+	EOF
+	cat >expect <<-\EOF &&
+	(NULL)
+	EOF
+	test-tool config configset_get_value a.key my.config >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'find value from a configset' '
 	cat >config2 <<-\EOF &&
 	[case]
-- 
2.39.0.rc0.955.ge9b241be664