Separate the instantiation and initialisation of the stores

Add a new `init()` method to the `Store` class that is supposed to
handle all the effectful initialisation needed to set-up the store.
The constructor should remain side-effect free and just initialize the
c++ data structure.

The goal behind that is that we can create “dummy” instances of each
store to query static properties about it (the parameters it accepts for
example)

1 files changed, 4 insertions, 0 deletions

diff --git a/src/libstore/dummy-store.cc b/src/libstore/dummy-store.cc
index dd1880877..52086445e 100644
--- a/src/libstore/dummy-store.cc
+++ b/src/libstore/dummy-store.cc
@@ -5,6 +5,10 @@ namespace nix {
 struct DummyStore : public Store
 {
     DummyStore(const std::string uri, const Params & params)
+        : DummyStore(params)
+    { }
+
+    DummyStore(const Params & params)
         : Store(params)
     { }