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, 6 insertions, 4 deletions

diff --git a/src/libstore/binary-cache-store.hh b/src/libstore/binary-cache-store.hh
index d42b1abd2455..5c2d0acfdbb7 100644
--- a/src/libstore/binary-cache-store.hh
+++ b/src/libstore/binary-cache-store.hh
@@ -13,13 +13,15 @@ struct NarInfo;
 
 class BinaryCacheStore : public Store
 {
-private:
+public:
 
-    std::unique_ptr<SecretKey> secretKey;
+    const Setting<std::string> compression{this, "xz", "compression", "NAR compression method ('xz', 'bzip2', or 'none')"};
+    const Setting<bool> writeNARListing{this, false, "write-nar-listing", "whether to write a JSON file listing the files in each NAR"};
+    const Setting<Path> secretKeyFile{this, "", "secret-key", "path to secret key used to sign the binary cache"};
 
-    std::string compression;
+private:
 
-    bool writeNARListing;
+    std::unique_ptr<SecretKey> secretKey;
 
 protected: