[PATCH] config: fix case sensitive subsection names on writing

[Stefan Beller <sbeller@google.com>]

A use reported a submodule issue regarding strange case indentation
issues, but it could be boiled down to the following test case:

  $ git init test  && cd test
  $ git config foo."Bar".key test
  $ git config foo."bar".key test
  $ tail -n 3 .git/config
  [foo "Bar"]
        key = test
        key = test

Sub sections are case sensitive and we have a test for correctly reading
them. However we do not have a test for writing out config correctly with
case sensitive subsection names, which is why this went unnoticed in
6ae996f2acf (git_config_set: make use of the config parser's event
stream, 2018-04-09)

Make the subsection case sensitive and provide a test for writing.
The test for reading is just above this test.

Reported-by: JP Sugarbroad <jpsugar@google.com>
Signed-off-by: Stefan Beller <sbeller@google.com>
---

I really appreciate the work by DScho (and Peff as I recall him as an active
reviewer there) on 4f4d0b42bae (Merge branch 'js/empty-config-section-fix',
2018-05-08), as the corner cases are all correct, modulo the one line fix
in this patch.

Thanks,
Stefan

 config.c          |  2 +-
 t/t1300-config.sh | 57 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/config.c b/config.c
index 7968ef7566a..de646d2c56f 100644
--- a/config.c
+++ b/config.c
@@ -2362,7 +2362,7 @@ static int store_aux_event(enum config_event_t type,
 		store->is_keys_section =
 			store->parsed[store->parsed_nr].is_keys_section =
 			cf->var.len - 1 == store->baselen &&
-			!strncasecmp(cf->var.buf, store->key, store->baselen);
+			!strncmp(cf->var.buf, store->key, store->baselen);
 		if (store->is_keys_section) {
 			store->section_seen = 1;
 			ALLOC_GROW(store->seen, store->seen_nr + 1,
diff --git a/t/t1300-config.sh b/t/t1300-config.sh
index 03c223708eb..710e2b04ad8 100755
--- a/t/t1300-config.sh
+++ b/t/t1300-config.sh
@@ -1218,6 +1218,63 @@ test_expect_success 'last one wins: three level vars' '
 	test_cmp expect actual
 '
 
+test_expect_success 'old-fashioned settings are case insensitive' '
+	test_when_finished "rm -f testConfig testConfig_expect testConfig_actual" &&
+
+	cat >testConfig <<-EOF &&
+		# insensitive:
+		[V.A]
+		r = value1
+	EOF
+	q_to_tab >testConfig_expect <<-EOF &&
+		# insensitive:
+		[V.A]
+		Qr = value2
+	EOF
+
+	for key in "v.a.r" "V.A.r" "v.A.r" "V.a.r"
+	do
+		cp testConfig testConfig_actual &&
+		git config -f testConfig_actual v.a.r value2 &&
+		test_cmp testConfig_expect testConfig_actual
+	done
+'
+
+test_expect_success 'setting different case sensitive subsections ' '
+	test_when_finished "rm -f testConfig testConfig_expect testConfig_actual" &&
+
+	cat >testConfig <<-EOF &&
+		# V insensitive A sensitive:
+		[V "A"]
+		r = value1
+		# same as above:
+		[V "a"]
+		r = value2
+	EOF
+
+	git config -f testConfig v.a.r value3 &&
+	q_to_tab >testConfig_expect <<-EOF &&
+		# V insensitive A sensitive:
+		[V "A"]
+		r = value1
+		# same as above:
+		[V "a"]
+		Qr = value3
+	EOF
+	test_cmp testConfig_expect testConfig &&
+
+	git config -f testConfig v.A.r value4 &&
+	q_to_tab >testConfig_expect <<-EOF &&
+		# V insensitive A sensitive:
+		[V "A"]
+		Qr = value4
+		# same as above:
+		[V "a"]
+		Qr = value3
+	EOF
+	test_cmp testConfig_expect testConfig
+'
+
 for VAR in a .a a. a.0b a."b c". a."b c".0d
 do
 	test_expect_success "git -c $VAR=VAL rejects invalid '$VAR'" '
-- 
2.18.0.345.g5c9ce644c3-goog