+/*
+ * Auxiliary function to sanity-check and split the key into the section
+ * identifier and variable name.
+ *
+ * Returns 0 on success, -1 when there is an invalid character in the key and
+ * -2 if there is no section name in the key.
+ *
+ * store_key - pointer to char* which will hold a copy of the key with
+ * lowercase section and variable name
+ * baselen - pointer to int which will hold the length of the
+ * section + subsection part, can be NULL
+ */
+int git_config_parse_key(const char *key, char **store_key, int *baselen_)
+{
+ int i, dot, baselen;
+ const char *last_dot = strrchr(key, '.');
+
+ /*
+ * Since "key" actually contains the section name and the real
+ * key name separated by a dot, we have to know where the dot is.
+ */
+
+ if (last_dot == NULL) {
+ error("key does not contain a section: %s", key);
+ return -2;
+ }
+
+ baselen = last_dot - key;
+ if (baselen_)
+ *baselen_ = baselen;
+
+ /*
+ * Validate the key and while at it, lower case it for matching.
+ */
+ *store_key = xmalloc(strlen(key) + 1);
+
+ dot = 0;
+ for (i = 0; key[i]; i++) {
+ unsigned char c = key[i];
+ if (c == '.')
+ dot = 1;
+ /* Leave the extended basename untouched.. */
+ if (!dot || i > baselen) {
+ if (!iskeychar(c) ||
+ (i == baselen + 1 && !isalpha(c))) {
+ error("invalid key: %s", key);
+ goto out_free_ret_1;
+ }
+ c = tolower(c);
+ } else if (c == '\n') {
+ error("invalid key (newline): %s", key);
+ goto out_free_ret_1;
+ }
+ (*store_key)[i] = c;
+ }
+ (*store_key)[i] = 0;
+
+ return 0;
+
+out_free_ret_1:
+ free(*store_key);
+ return -1;
+}
+