Add StoreURI::render

This will be needed for the next step.

src/libstore/store-reference.cc

@@ -4,6 +4,7 @@
 #include "url.hh"
 #include "store-reference.hh"
 #include "file-system.hh"
+#include "util.hh"
 
 namespace nix {
 
@@ -17,6 +18,26 @@ static bool isNonUriPath(const std::string & spec)
         && spec.find("/") != std::string::npos;
 }
 
+std::string StoreReference::render() const
+{
+    std::string res;
+
+    std::visit(
+        overloaded{
+            [&](const StoreReference::Auto &) { res = "auto"; },
+            [&](const StoreReference::Specified & g) {
+                res = g.scheme;
+                res += "://";
+                res += g.authority;
+            },
+        },
+        variant);
+
+    res += encodeQuery(params);
+
+    return res;
+}
+
 StoreReference StoreReference::parse(const std::string & uri, const StoreReference::Params & extraParams)
 {
     auto params = extraParams;

src/libstore/store-reference.hh

@@ -70,6 +70,8 @@ struct StoreReference
 
     auto operator<=>(const StoreReference & rhs) const = default;
 
+    std::string render() const;
+
     static StoreReference parse(const std::string & uri, const Params & extraParams = Params{});
 };
 

src/libutil/url.hh

@@ -33,6 +33,8 @@ std::string percentEncode(std::string_view s, std::string_view keep="");
 
 std::map<std::string, std::string> decodeQuery(const std::string & query);
 
+std::string encodeQuery(const std::map<std::string, std::string> & query);
+
 ParsedURL parseURL(const std::string & url);
 
 /**