[PATCH 2/3] config: fix case sensitive subsection names on writing

[Stefan Beller <sbeller@xxxxxxxxxx>]

A user reported a submodule issue regarding a section mix-up,
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)

Unfortunately we have to make a distinction between old style configuration
that looks like

  [foo.Bar]
        key = test

and the new quoted style as seen above. The old style is documented as
case-agnostic, hence we need to keep 'strncasecmp'; although the
resulting setting for the old style config differs from the configuration.
That will be fixed in a follow up patch.

Reported-by: JP Sugarbroad <jpsugar@xxxxxxxxxx>
Signed-off-by: Stefan Beller <sbeller@xxxxxxxxxx>
---
 config.c          | 12 +++++++++++-
 t/t1300-config.sh |  1 +
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/config.c b/config.c
index 66645047eb3..ffc2ffeafeb 100644
--- a/config.c
+++ b/config.c
@@ -37,6 +37,7 @@ struct config_source {
 	int eof;
 	struct strbuf value;
 	struct strbuf var;
+	unsigned section_name_old_dot_style : 1;
 
 	int (*do_fgetc)(struct config_source *c);
 	int (*do_ungetc)(int c, struct config_source *conf);
@@ -605,6 +606,7 @@ static int get_value(config_fn_t fn, void *data, struct strbuf *name)
 
 static int get_extended_base_var(struct strbuf *name, int c)
 {
+	cf->section_name_old_dot_style = 0;
 	do {
 		if (c == '\n')
 			goto error_incomplete_line;
@@ -641,6 +643,7 @@ static int get_extended_base_var(struct strbuf *name, int c)
 
 static int get_base_var(struct strbuf *name)
 {
+	cf->section_name_old_dot_style = 1;
 	for (;;) {
 		int c = get_next_char();
 		if (cf->eof)
@@ -2364,14 +2367,21 @@ static int store_aux_event(enum config_event_t type,
 	store->parsed[store->parsed_nr].type = type;
 
 	if (type == CONFIG_EVENT_SECTION) {
+		int (*cmpfn)(const char *, const char *, size_t);
+
 		if (cf->var.len < 2 || cf->var.buf[cf->var.len - 1] != '.')
 			return error("invalid section name '%s'", cf->var.buf);
 
+		if (cf->section_name_old_dot_style)
+			cmpfn = strncasecmp;
+		else
+			cmpfn = strncmp;
+
 		/* Is this the section we were looking for? */
 		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);
+			!cmpfn(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 e87cfc1804f..4976e2fcd3f 100755
--- a/t/t1300-config.sh
+++ b/t/t1300-config.sh
@@ -1290,6 +1290,7 @@ test_expect_success 'setting different case sensitive subsections ' '
 		Qc = v2
 		[d "e"]
 		f = v1
+		[d "E"]
 		Qf = v2
 	EOF
 	# exact match
-- 
2.18.0.132.g195c49a2227