$ git grep flake src/libfetchers/
src/libfetchers/fetch-settings.hh:          Example `~/code/flake.nix`:
src/libfetchers/fetch-settings.hh:    Setting<std::string> flakeRegistry{this, "https://channels.nixos.org/flake-registry.json", "flake-registry",
src/libfetchers/fetch-settings.hh:          Path or URI of the global flake registry.
src/libfetchers/fetch-settings.hh:          When empty, disables the global flake registry.
src/libfetchers/fetch-settings.hh:        "Whether to use flake registries to resolve flake references.",
src/libfetchers/fetch-settings.hh:    Setting<bool> acceptFlakeConfig{this, false, "accept-flake-config",
src/libfetchers/fetch-settings.hh:        "Whether to accept nix configuration from a flake without prompting.",
src/libfetchers/fetch-settings.hh:          The commit summary to use when committing changed flake lock files. If
src/libfetchers/fetchers.cc:            // usages (e.g. `builtins.fetchTree` calls or flake inputs).
src/libfetchers/indirect.cc:std::regex flakeRegex("[a-zA-Z][a-zA-Z0-9_-]*", std::regex::ECMAScript);
src/libfetchers/indirect.cc:        if (url.scheme != "flake") return {};
src/libfetchers/indirect.cc:                throw BadURL("in flake URL '%s', '%s' is not a commit hash or branch/tag name", url.url, path[1]);
src/libfetchers/indirect.cc:                throw BadURL("in flake URL '%s', '%s' is not a branch/tag name", url.url, path[1]);
src/libfetchers/indirect.cc:                throw BadURL("in flake URL '%s', '%s' is not a commit hash", url.url, path[2]);
src/libfetchers/indirect.cc:        if (!std::regex_match(id, flakeRegex))
src/libfetchers/indirect.cc:            throw BadURL("'%s' is not a valid flake ID", id);
src/libfetchers/indirect.cc:        if (!std::regex_match(id, flakeRegex))
src/libfetchers/indirect.cc:            throw BadURL("'%s' is not a valid flake ID", id);
src/libfetchers/indirect.cc:        url.scheme = "flake";
src/libfetchers/registry.cc:            for (auto & i : json["flakes"]) {
src/libfetchers/registry.cc:            throw Error("flake registry '%s' has unsupported version %d", path, version);
src/libfetchers/registry.cc:        warn("cannot parse flake registry '%s': %s", path, e.what());
src/libfetchers/registry.cc:        warn("cannot read flake registry '%s': %s", path, e.what());
src/libfetchers/registry.cc:    json["flakes"] = std::move(arr);
src/libfetchers/registry.cc:        auto path = fetchSettings.flakeRegistry.get();
src/libfetchers/registry.cc:            auto storePath = downloadFile(store, path, "flake-registry.json", false).storePath;
src/libfetchers/registry.cc:                store2->addPermRoot(storePath, getCacheDir() + "/nix/flake-registry.json");
src/libfetchers/registry.cc:    if (n > 100) throw Error("cycle detected in flake registry for '%s'", input.to_string());
src/libfetchers/registry.cc:        throw Error("cannot find flake '%s' in the flake registries", input.to_string());
src/libfetchers/tarball.cc:            // FIXME: would be nice to support arbitrary flakerefs
src/libfetchers/tarball.cc:            // here, e.g. git flakes.