Don't just accept git-forbidden tags about crap HOT 1 OPEN

bool tag_name_is_valid(const char* restrict str, size_t len)
{
	// Rules as appear here:
	// https://stackoverflow.com/a/26382358/1593077

	// rule 1
	if (str[0] == '.') { return false; }
	if (strstr(str, "/.")) { return false; }
	if (strstr(str, ".lock/")) { return false; }
	if (strcmp(str + len - 5, ".lock") == 0) { return false; }
	// rule 2 - unused, since theoretically we could have "allow-onelevel"
	// if (strchr(str, '/') == NULL) { return false; }
	// rule 3
	if (strstr(str, "..")) { return false; }
	// rule 4
	for(size_t i; i < len; i++) {
		char c = str[i];
		bool is_ascii_control_char = (c < 0x20) || (c == 0x7F /* DEL */);
		if (is_ascii_control_char || c == ' ' || c == '~' || c == '^' || c ==':' ) return false;
	}
	// rule 4
	if ( (strpbrk(str, "?*[") != NULL) ) { return false; }
	// rule 5
	if ( (strpbrk(str, "?*[") != NULL) ) { return false; }
	// rule 6
	if ( (str[0]) || (str[len - 1] == '/') || (strstr(str, "//") != NULL) ) { return false; }
	// rule 7
	if (str[len - 1] == '.') { return false; }
	// rule 8
	if (strchr(str,"@{") != NULL) { return false; }
	// rule 9
	if (str[0] == '@' && len == 1) { return false; }
	// rule 10
	if (strchr(str, '\\') != NULL) { return false; }
	return true;
}