Deprecate the online flake registries and vendor the default registry

Fixes #183, #110, #116.

The default flake-registry option becomes 'vendored', and refers
to a vendored flake-registry.json file in the install path.

Vendored copy of the flake-registry is from github:NixOS/flake-registry
at commit 9c69f7bd2363e71fe5cd7f608113290c7614dcdd.

Change-Id: I752b81c85ebeaab4e582ac01c239d69d65580f37

2 files changed, 13 insertions, 2 deletions

diff --git a/src/libfetchers/fetch-settings.hh b/src/libfetchers/fetch-settings.hh
index 6108a179c..c67a75082 100644
--- a/src/libfetchers/fetch-settings.hh
+++ b/src/libfetchers/fetch-settings.hh
@@ -71,10 +71,13 @@ struct FetchSettings : public Config
     Setting<bool> warnDirty{this, true, "warn-dirty",
         "Whether to warn about dirty Git/Mercurial trees."};
 
-    Setting<std::string> flakeRegistry{this, "https://channels.nixos.org/flake-registry.json", "flake-registry",
+    Setting<std::string> flakeRegistry{this, "vendored", "flake-registry",
         R"(
           Path or URI of the global flake registry.
 
+          URIs are deprecated. When set to 'vendored', defaults to a vendored
+          copy of https://channels.nixos.org/flake-registry.json.
+
           When empty, disables the global flake registry.
         )",
         {}, true, Xp::Flakes};
diff --git a/src/libfetchers/registry.cc b/src/libfetchers/registry.cc
index da92273d6..4b2d61f52 100644
--- a/src/libfetchers/registry.cc
+++ b/src/libfetchers/registry.cc
@@ -16,8 +16,12 @@ std::shared_ptr<Registry> Registry::read(
 {
     auto registry = std::make_shared<Registry>(type);
 
-    if (!pathExists(path))
+    if (!pathExists(path)) {
+        if (type == RegistryType::Global) {
+            warn("cannot read flake registry '%s': path does not exist", path);
+        }
         return std::make_shared<Registry>(type);
+    }
 
     try {
 
@@ -155,9 +159,13 @@ static std::shared_ptr<Registry> getGlobalRegistry(ref<Store> store)
         auto path = fetchSettings.flakeRegistry.get();
         if (path == "") {
             return std::make_shared<Registry>(Registry::Global); // empty registry
+        } else if (path == "vendored") {
+            return Registry::read(settings.nixDataDir + "/flake-registry.json", Registry::Global);
         }
 
         if (!path.starts_with("/")) {
+            warn("config option flake-registry referring to a URL is deprecated and will be removed in Lix 3.0; yours is: `%s'", path);
+
             auto storePath = downloadFile(store, path, "flake-registry.json", false).storePath;
             if (auto store2 = store.dynamic_pointer_cast<LocalFSStore>())
                 store2->addPermRoot(storePath, getCacheDir() + "/nix/flake-registry.json");