[PATCH v2 1/2] document irregular config --add behaviour for empty and NULL values

If we have a config file like,
[foo]
        baz
        bar =

and we try something like, "git config --add foo.baz roll", Git will
segfault. Moreover, for "git config --add foo.bar roll", it will
overwrite the original value instead of appending after the existing
empty value. Document these deficiencies in form of a test.

Helped-by: Junio C Hamano [off-list ref]
Signed-off-by: Tanay Abhra <redacted>
---

Sorry for this very late reply. I was stuck in a flood affected region
with no internet connectivity for the past week. I am safe now. :)

FWIW, here is the reroll with a set bit in the store struct and an exported
global. I could have done the reroll as you have done, but Jeff had mentioned
that he liked the version with a bit flag more. But you can choose the version
that seems better to you.

 t/t1303-wacky-config.sh | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/t/t1303-wacky-config.sh b/t/t1303-wacky-config.sh
index 3a2c819..e5c0f07 100755
--- a/t/t1303-wacky-config.sh
+++ b/t/t1303-wacky-config.sh

@@ -111,4 +111,24 @@ test_expect_success 'unset many entries' '
 	test_must_fail git config section.key
 '

+test_expect_failure '--add appends new value after existing empty value' '
+	cat >expect <<-\EOF &&
+
+
+	fool
+	roll
+	EOF
+	cp .git/config .git/config.old &&
+	test_when_finished "mv .git/config.old .git/config" &&
+	cat >.git/config <<-\EOF &&
+	[foo]
+		baz
+		baz =
+		baz = fool
+	EOF
+	git config --add foo.baz roll &&
+	git config --get-all foo.baz >output &&
+	test_cmp expect output
+'
+
 test_done

-- 
1.9.0.GIT