Add a test for Nix store optimisation

tests/Makefile.am

@@ -9,7 +9,7 @@ TESTS = init.sh hash.sh lang.sh add.sh simple.sh dependencies.sh \
   gc-runtime.sh install-package.sh check-refs.sh filter-source.sh \
   remote-store.sh export.sh export-graph.sh negative-caching.sh \
   binary-patching.sh timeout.sh secure-drv-outputs.sh nix-channel.sh \
-  multiple-outputs.sh import-derivation.sh fetchurl.sh
+  multiple-outputs.sh import-derivation.sh fetchurl.sh optimise-store.sh
 
 XFAIL_TESTS =
 

tests/optimise-store.sh

@@ -0,0 +1,26 @@
+source common.sh
+
+clearStore
+
+outPath1=$(echo 'with import ./config.nix; mkDerivation { name = "foo1"; builder = builtins.toFile "builder" "mkdir $out; echo hello > $out/foo"; }' | nix-build - --no-out-link)
+outPath2=$(echo 'with import ./config.nix; mkDerivation { name = "foo2"; builder = builtins.toFile "builder" "mkdir $out; echo hello > $out/foo"; }' | nix-build - --no-out-link)
+
+inode1="$(perl -e "print ((lstat('$outPath1/foo'))[1])")"
+inode2="$(perl -e "print ((lstat('$outPath2/foo'))[1])")"
+if [ "$inode1" != "$inode2" ]; then
+    echo "inodes do not match"
+    exit 1
+fi
+
+nlink="$(perl -e "print ((lstat('$outPath1/foo'))[3])")"
+if [ "$nlink" != 3 ]; then
+    echo "link count incorrect"
+    exit 1
+fi
+
+nix-store --gc
+
+if [ -n "$(ls $NIX_STORE_DIR/.links)" ]; then
+    echo ".links directory not empty after GC"
+    exit 1
+fi