Move signPathInfo to Store

Motivation is the same for moving `signRealisation` in
db8439c.

Author: Ericson2314

src/libstore/local-store.cc

@@ -1585,20 +1585,6 @@ void LocalStore::addSignatures(const StorePath & storePath, const StringSet & si
 }
 
 
-void LocalStore::signPathInfo(ValidPathInfo & info)
-{
-    // FIXME: keep secret keys in memory.
-
-    auto secretKeyFiles = settings.secretKeyFiles;
-
-    for (auto & secretKeyFile : secretKeyFiles.get()) {
-        SecretKey secretKey(readFile(secretKeyFile));
-        LocalSigner signer(std::move(secretKey));
-        info.sign(*this, signer);
-    }
-}
-
-
 std::optional<std::pair<int64_t, Realisation>> LocalStore::queryRealisationCore_(
         LocalStore::State & state,
         const DrvOutput & id)

src/libstore/local-store.hh

@@ -396,12 +396,6 @@ private:
     bool isValidPath_(State & state, const StorePath & path);
     void queryReferrers(State & state, const StorePath & path, StorePathSet & referrers);
 
-    /**
-     * Add signatures to a ValidPathInfo or Realisation using the secret keys
-     * specified by the ‘secret-key-files’ option.
-     */
-    void signPathInfo(ValidPathInfo & info);
-
     void addBuildLog(const StorePath & drvPath, std::string_view log) override;
 
     friend struct LocalDerivationGoal;

src/libstore/store-api.cc

@@ -1274,6 +1274,21 @@ Derivation Store::readDerivation(const StorePath & drvPath)
 Derivation Store::readInvalidDerivation(const StorePath & drvPath)
 { return readDerivationCommon(*this, drvPath, false); }
 
+
+void Store::signPathInfo(ValidPathInfo & info)
+{
+    // FIXME: keep secret keys in memory.
+
+    auto secretKeyFiles = settings.secretKeyFiles;
+
+    for (auto & secretKeyFile : secretKeyFiles.get()) {
+        SecretKey secretKey(readFile(secretKeyFile));
+        LocalSigner signer(std::move(secretKey));
+        info.sign(*this, signer);
+    }
+}
+
+
 void Store::signRealisation(Realisation & realisation)
 {
     // FIXME: keep secret keys in memory.

src/libstore/store-api.hh

@@ -622,6 +622,12 @@ public:
     virtual void addSignatures(const StorePath & storePath, const StringSet & sigs)
     { unsupported("addSignatures"); }
 
+    /**
+     * Add signatures to a ValidPathInfo or Realisation using the secret keys
+     * specified by the ‘secret-key-files’ option.
+     */
+    void signPathInfo(ValidPathInfo & info);
+
     void signRealisation(Realisation &);
 
     /* Utility functions. */