Clone for Derivation

And `as_ptr` too.

This will be tested once we get the harmonia bindings in.

nix-bindings-store/src/derivation.rs

@@ -14,6 +14,38 @@ impl Derivation {
     pub(crate) fn new_raw(inner: NonNull<raw::derivation>) -> Self {
         Derivation { inner }
     }
+
+    /// This is a low level function that you shouldn't have to call unless you are developing the Nix bindings.
+    ///
+    /// Construct a new `Derivation` by first cloning the C derivation.
+    ///
+    /// # Safety
+    ///
+    /// This does not take ownership of the C derivation, so it should be a borrowed pointer, or you should free it.
+    pub unsafe fn new_raw_clone(inner: NonNull<raw::derivation>) -> Self {
+        Self::new_raw(
+            NonNull::new(raw::derivation_clone(inner.as_ptr()))
+                .or_else(|| panic!("nix_derivation_clone returned a null pointer"))
+                .unwrap(),
+        )
+    }
+
+    /// This is a low level function that you shouldn't have to call unless you are developing the Nix bindings.
+    ///
+    /// Get a pointer to the underlying Nix C API derivation.
+    ///
+    /// # Safety
+    ///
+    /// This function is unsafe because it returns a raw pointer. The caller must ensure that the pointer is not used beyond the lifetime of this `Derivation`.
+    pub unsafe fn as_ptr(&self) -> *mut raw::derivation {
+        self.inner.as_ptr()
+    }
+}
+
+impl Clone for Derivation {
+    fn clone(&self) -> Self {
+        unsafe { Self::new_raw_clone(self.inner) }
+    }
 }
 
 impl Drop for Derivation {