declare explicit const when possible

src/nix-eval-jobs.cc

@@ -469,7 +469,7 @@ auto main(int argc, char **argv) -> int {
                         job_json["constituents"] = nlohmann::json::array();
                     }
                     std::vector<std::string> errors;
-                    for (auto child : *namedConstituents) {
+                    for (const auto &child : *namedConstituents) {
                         auto childJob = state->jobs.find(child);
                         if (childJob == state->jobs.end()) {
                             broken = true;
@@ -522,7 +522,7 @@ auto main(int argc, char **argv) -> int {
                             nix::writeDerivation(*store, drvAggregate));
 
                         if (myArgs.gcRootsDir != "") {
-                            nix::Path root =
+                            const nix::Path root =
                                 myArgs.gcRootsDir + "/" +
                                 std::string(nix::baseNameOf(newDrvPath));
                             if (!nix::pathExists(root)) {

src/worker.cc

@@ -147,13 +147,13 @@ void worker(
                     if (args.constituents) {
                         std::vector<std::string> constituents;
                         std::vector<std::string> namedConstituents;
-                        auto a = v->attrs()->get(
+                        const auto *a = v->attrs()->get(
                             state->symbols.create("_hydraAggregate"));
                         if (a &&
                             state->forceBool(*a->value, a->pos,
                                              "while evaluating the "
                                              "`_hydraAggregate` attribute")) {
-                            auto a = v->attrs()->get(
+                            const auto *a = v->attrs()->get(
                                 state->symbols.create("constituents"));
                             if (!a)
                                 state
@@ -167,7 +167,7 @@ void worker(
                                 a->pos, *a->value, context,
                                 "while evaluating the `constituents` attribute",
                                 true, false);
-                            for (auto &c : context)
+                            for (const auto &c : context) {
                                 std::visit(
                                     nix::overloaded{
                                         [&](const nix::NixStringContextElem::