* Add missing files to dist.

* Fix GC and substitute bugs related to self-references.  Add a
  regression test.

src/libstore/build.cc

@@ -1329,6 +1329,7 @@ void SubstitutionGoal::init()
 
     for (PathSet::iterator i = references.begin();
          i != references.end(); ++i)
+        if (*i != storePath) /* ignore self-references */
             addWaitee(worker.makeSubstitutionGoal(*i));
 
     if (waitees.empty()) /* to prevent hang (no wake-up event) */
@@ -1347,6 +1348,7 @@ void SubstitutionGoal::referencesValid()
 
     for (PathSet::iterator i = references.begin();
          i != references.end(); ++i)
+        if (*i != storePath) /* ignore self-references */
             assert(isValidPath(*i));
     
     tryNext();

src/libstore/store.cc

@@ -553,7 +553,10 @@ void deleteFromStore(const Path & _path)
 
     Transaction txn(nixDB);
     if (isValidPathTxn(txn, path)) {
-        if (getReferers(txn, path).size() > 0)
+        PathSet referers = getReferers(txn, path);
+        if (referers.size() > 1 ||
+            (referers.size() == 1 &&
+                *referers.begin() != path))
             throw Error(format("cannot delete path `%1%' because it is in use") % path);
         invalidatePath(path, txn);
     }

tests/Makefile.am

@@ -39,7 +39,7 @@ gc-concurrent.sh: gc-concurrent.nix gc-concurrent2.nix
 TESTS = init.sh hash.sh lang.sh simple.sh dependencies.sh locking.sh parallel.sh \
   build-hook.sh substitutes.sh substitutes2.sh fallback.sh nix-push.sh gc.sh \
   gc-concurrent.sh verify.sh nix-pull.sh
-#TESTS = init.sh gc-concurrent.sh 
+#TESTS = init.sh nix-push.sh nix-pull.sh
 
 XFAIL_TESTS =
 
@@ -57,5 +57,6 @@ EXTRA_DIST = $(TESTS) \
   substitutes.nix.in substituter.sh \
   substitutes2.nix.in substituter2.sh \
   gc-concurrent.nix.in gc-concurrent.builder.sh \
+  gc-concurrent2.nix.in gc-concurrent2.builder.sh \
   fallback.nix.in \
   $(wildcard lang/*.nix) $(wildcard lang/*.exp)

tests/dependencies.builder0.sh

@@ -4,3 +4,6 @@ mkdir $out
 echo $(cat $input1/foo)$(cat $input2/bar) > $out/foobar
 
 ln -s $input2 $out/input-2
+
+# Self-reference.
+ln -s $out $out/self