From 8972f7c14a196041f8faef2f2c3f7bd705ab4e07 Mon Sep 17 00:00:00 2001
From: Luca Bruno <lucabru@src.gnome.org>
Date: Wed, 6 May 2015 15:16:35 +0000
Subject: [PATCH] nix-collect-garbage: Do not pass an empty argument. Closes
 #530

---
 src/nix-collect-garbage/nix-collect-garbage.cc | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/nix-collect-garbage/nix-collect-garbage.cc b/src/nix-collect-garbage/nix-collect-garbage.cc
index 366a378a1..ae75fd621 100644
--- a/src/nix-collect-garbage/nix-collect-garbage.cc
+++ b/src/nix-collect-garbage/nix-collect-garbage.cc
@@ -45,7 +45,11 @@ void removeOldGenerations(std::string dir)
             if (link.find("link") != string::npos) {
                 printMsg(lvlInfo, format("removing old generations of profile %1%") % path);
 
-                runProgramSimple(settings.nixBinDir + "/nix-env", Strings{"-p", path, "--delete-generations", gen, dryRun ? "--dry-run" : ""});
+                auto args = Strings{"-p", path, "--delete-generations", gen};
+                if (dryRun) {
+                    args.push_back("--dry-run");
+                }
+                runProgramSimple(settings.nixBinDir + "/nix-env", args);
             }
         } else if (type == DT_DIR) {
             removeOldGenerations(path);