nix path-info -r: Don't duplicate the root paths

This fixes

  $ nix path-info -r $(type -P ls)
  /nix/store/vfilzcp8a467w3p0mp54ybq6bdzb8w49-coreutils-8.32
  /nix/store/5d821pjgzb90lw4zbg6xwxs7llm335wr-libunistring-0.9.10
  ...
  /nix/store/mrv4y369nw6hg4pw8d9p9bfdxj9pjw0x-acl-2.3.0
  /nix/store/vfilzcp8a467w3p0mp54ybq6bdzb8w49-coreutils-8.32

Also, output the paths in topologically sorted order like we used to.

1 files changed, 9 insertions, 6 deletions

diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 2b9902677..0d61e12d0 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -120,7 +120,7 @@ void BuiltPathsCommand::run(ref<Store> store)
             // XXX: This only computes the store path closure, ignoring
             // intermediate realisations
             StorePathSet pathsRoots, pathsClosure;
-            for (auto & root: paths) {
+            for (auto & root : paths) {
                 auto rootFromThis = root.outPaths();
                 pathsRoots.insert(rootFromThis.begin(), rootFromThis.end());
             }
@@ -140,12 +140,15 @@ StorePathsCommand::StorePathsCommand(bool recursive)
 
 void StorePathsCommand::run(ref<Store> store, BuiltPaths && paths)
 {
-    StorePaths storePaths;
-    for (auto& builtPath : paths)
-        for (auto& p : builtPath.outPaths())
-            storePaths.push_back(p);
+    StorePathSet storePaths;
+    for (auto & builtPath : paths)
+        for (auto & p : builtPath.outPaths())
+            storePaths.insert(p);
 
-    run(store, std::move(storePaths));
+    auto sorted = store->topoSortPaths(storePaths);
+    std::reverse(sorted.begin(), sorted.end());
+
+    run(store, std::move(sorted));
 }
 
 void StorePathCommand::run(ref<Store> store, std::vector<StorePath> && storePaths)