config: write out section headers with subsections correctly

write_section() mistakenly treated is input as the whole variable name
instead of simply the section (and possibly subsection) and would
confuse "section.subsection" as a section plus variable name and
produce a wrong section header.

Fix this and include a test for writing "section.subsection.var" and
reading it from the file.

src/config_file.c

@@ -925,22 +925,18 @@ static int config_parse(diskfile_backend *cfg_file)
 static int write_section(git_filebuf *file, const char *key)
 {
 	int error;
-	const char *fdot, *ldot;
+	const char *dot;
 	git_buf buf = GIT_BUF_INIT;
 
 	/* All of this just for [section "subsection"] */
-	fdot = strchr(key, '.');
+	dot = strchr(key, '.');
 	git_buf_putc(&buf, '[');
-	if (fdot == NULL)
+	if (dot == NULL) {
 		git_buf_puts(&buf, key);
-	else
-		git_buf_put(&buf, key, fdot - key);
-	ldot = strrchr(key, '.');
-	if (fdot != ldot && fdot != NULL) {
-		git_buf_putc(&buf, '"');
+	} else {
+		git_buf_put(&buf, key, dot - key);
 		/* TODO: escape  */
-		git_buf_put(&buf, fdot + 1, ldot - fdot - 1);
-		git_buf_putc(&buf, '"');
+		git_buf_printf(&buf, " \"%s\"", dot + 1);
 	}
 	git_buf_puts(&buf, "]\n");
 	if (git_buf_oom(&buf))

tests-clar/config/write.c

@@ -67,6 +67,21 @@ void test_config_write__delete_value(void)
 	git_config_free(cfg);
 }
 
+void test_config_write__write_subsection(void)
+{
+	git_config *cfg;
+	const char *str;
+
+	cl_git_pass(git_config_open_ondisk(&cfg, "config9"));
+	cl_git_pass(git_config_set_string(cfg, "my.own.var", "works"));
+	git_config_free(cfg);
+
+	cl_git_pass(git_config_open_ondisk(&cfg, "config9"));
+	cl_git_pass(git_config_get_string(cfg, "my.own.var", &str));
+	cl_git_pass(strcmp(str, "works"));
+	git_config_free(cfg);
+}
+
 void test_config_write__delete_inexistent(void)
 {
 	git_config *cfg;