Add priority setting to stores

This allows overriding the priority of substituters, e.g.

  $ nix-store --store ~/my-nix/ -r /nix/store/df3m4da96d84ljzxx4mygfshm1p0r2n3-geeqie-1.4 \
    --substituters 'http://cache.nixos.org?priority=100 daemon?priority=10'

Fixes #3264.

1 files changed, 5 insertions, 3 deletions

diff --git a/src/libutil/config.hh b/src/libutil/config.hh
index d86c65ff0..7ea78fdaf 100644
--- a/src/libutil/config.hh
+++ b/src/libutil/config.hh
@@ -115,6 +115,8 @@ public:
 
     bool overriden = false;
 
+    void setDefault(const std::string & str);
+
 protected:
 
     AbstractSetting(
@@ -131,13 +133,13 @@ protected:
 
     virtual void set(const std::string & value) = 0;
 
-    virtual std::string to_string() = 0;
+    virtual std::string to_string() const = 0;
 
     virtual void toJSON(JSONPlaceholder & out);
 
     virtual void convertToArg(Args & args, const std::string & category);
 
-    bool isOverriden() { return overriden; }
+    bool isOverriden() const { return overriden; }
 };
 
 /* A setting of type T. */
@@ -174,7 +176,7 @@ public:
         value = v;
     }
 
-    std::string to_string() override;
+    std::string to_string() const override;
 
     void convertToArg(Args & args, const std::string & category) override;