* Maintain the references/referers relation also for derivations.

This simplifies garbage collection and `nix-store --query
  --requisites' since we no longer need to treat derivations
  specially.

* Better maintaining of the invariants, e.g., setReferences() can only
  be called on a valid/substitutable path.

src/libstore/build.hh

@@ -28,23 +28,4 @@ Derivation derivationFromPath(const Path & drvPath);
 void computeFSClosure(const Path & storePath,
     PathSet & paths, bool flipDirection = false);
 
-/* Place in `paths' the set of paths that are required to `realise'
-   the given store path, i.e., all paths necessary for valid
-   deployment of the path.  For a derivation, this is the union of
-   requisites of the inputs, plus the derivation; for other store
-   paths, it is the set of paths in the FS closure of the path.  If
-   `includeOutputs' is true, include the requisites of the output
-   paths of derivations as well.
-
-   Note that this function can be used to implement three different
-   deployment policies:
-
-   - Source deployment (when called on a derivation).
-   - Binary deployment (when called on an output path).
-   - Source/binary deployment (when called on a derivation with
-     `includeOutputs' set to true).
-*/
-void storePathRequisites(const Path & storePath,
-    bool includeOutputs, PathSet & paths);
-
 #endif /* !__BUILD_H */