Add a Config class to simplify adding configuration settings

The typical use is to inherit Config and add Setting<T> members:

  class MyClass : private Config
  {
    Setting<int> foo{this, 123, "foo", "the number of foos to use"};
    Setting<std::string> bar{this, "blabla", "bar", "the name of the bar"};

    MyClass() : Config(readConfigFile("/etc/my-app.conf"))
    {
      std::cout << foo << "\n"; // will print 123 unless overriden
    }
  };

Currently, this is used by Store and its subclasses for store
parameters. You now get a warning if you specify a non-existant store
parameter in a store URI.

1 files changed, 3 insertions, 2 deletions

diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index 8610841d72..0ea897526b 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -38,13 +38,14 @@ namespace nix {
 LocalStore::LocalStore(const Params & params)
     : Store(params)
     , LocalFSStore(params)
-    , realStoreDir(get(params, "real", rootDir != "" ? rootDir + "/nix/store" : storeDir))
+    , realStoreDir_{this, false, rootDir != "" ? rootDir + "/nix/store" : storeDir, "real",
+        "physical path to the Nix store"}
+    , realStoreDir(realStoreDir_)
     , dbDir(stateDir + "/db")
     , linksDir(realStoreDir + "/.links")
     , reservedPath(dbDir + "/reserved")
     , schemaPath(dbDir + "/schema")
     , trashDir(realStoreDir + "/trash")
-    , requireSigs(trim(settings.get("signed-binary-caches", std::string("*"))) != "") // FIXME: rename option
     , publicKeys(getDefaultPublicKeys())
 {
     auto state(_state.lock());