Make clear that StorePathWithOutputs is a deprecated type

- Add a comment

- Put `OutputsSpec` in a different header (First part of #6815)

- Make a few stray uses of it in new code use `DerivedPath` instead.

src/libstore/path-with-outputs.cc

@@ -1,6 +1,5 @@
 #include "path-with-outputs.hh"
 #include "store-api.hh"
-#include "nlohmann/json.hpp"
 
 #include <regex>
 
@@ -71,57 +70,4 @@ StorePathWithOutputs followLinksToStorePathWithOutputs(const Store & store, std:
     return StorePathWithOutputs { store.followLinksToStorePath(path), std::move(outputs) };
 }
 
-std::pair<std::string, OutputsSpec> parseOutputsSpec(const std::string & s)
-{
-    static std::regex regex(R"((.*)\^((\*)|([a-z]+(,[a-z]+)*)))");
-
-    std::smatch match;
-    if (!std::regex_match(s, match, regex))
-        return {s, DefaultOutputs()};
-
-    if (match[3].matched)
-        return {match[1], AllOutputs()};
-
-    return {match[1], tokenizeString<OutputNames>(match[4].str(), ",")};
-}
-
-std::string printOutputsSpec(const OutputsSpec & outputsSpec)
-{
-    if (std::get_if<DefaultOutputs>(&outputsSpec))
-        return "";
-
-    if (std::get_if<AllOutputs>(&outputsSpec))
-        return "^*";
-
-    if (auto outputNames = std::get_if<OutputNames>(&outputsSpec))
-        return "^" + concatStringsSep(",", *outputNames);
-
-    assert(false);
-}
-
-void to_json(nlohmann::json & json, const OutputsSpec & outputsSpec)
-{
-    if (std::get_if<DefaultOutputs>(&outputsSpec))
-        json = nullptr;
-
-    else if (std::get_if<AllOutputs>(&outputsSpec))
-        json = std::vector<std::string>({"*"});
-
-    else if (auto outputNames = std::get_if<OutputNames>(&outputsSpec))
-        json = *outputNames;
-}
-
-void from_json(const nlohmann::json & json, OutputsSpec & outputsSpec)
-{
-    if (json.is_null())
-        outputsSpec = DefaultOutputs();
-    else {
-        auto names = json.get<OutputNames>();
-        if (names == OutputNames({"*"}))
-            outputsSpec = AllOutputs();
-        else
-            outputsSpec = names;
-    }
-}
-
 }