nix copy: Add --profile and --out-link flags

src/libcmd/command.cc

@@ -179,41 +179,45 @@ BuiltPathsCommand::BuiltPathsCommand(bool recursive)
 
 void BuiltPathsCommand::run(ref<Store> store, Installables && installables)
 {
-    BuiltPaths paths;
+    BuiltPaths rootPaths, allPaths;
+
     if (all) {
         if (installables.size())
             throw UsageError("'--all' does not expect arguments");
         // XXX: Only uses opaque paths, ignores all the realisations
         for (auto & p : store->queryAllValidPaths())
-            paths.emplace_back(BuiltPath::Opaque{p});
+            rootPaths.emplace_back(BuiltPath::Opaque{p});
+        allPaths = rootPaths;
     } else {
-        paths = Installable::toBuiltPaths(getEvalStore(), store, realiseMode, operateOn, installables);
+        rootPaths = Installable::toBuiltPaths(getEvalStore(), store, realiseMode, operateOn, installables);
+        allPaths = rootPaths;
+
         if (recursive) {
             // XXX: This only computes the store path closure, ignoring
             // intermediate realisations
             StorePathSet pathsRoots, pathsClosure;
-            for (auto & root : paths) {
+            for (auto & root : rootPaths) {
                 auto rootFromThis = root.outPaths();
                 pathsRoots.insert(rootFromThis.begin(), rootFromThis.end());
             }
             store->computeFSClosure(pathsRoots, pathsClosure);
             for (auto & path : pathsClosure)
-                paths.emplace_back(BuiltPath::Opaque{path});
+                allPaths.emplace_back(BuiltPath::Opaque{path});
         }
     }
 
-    run(store, std::move(paths));
+    run(store, std::move(allPaths), std::move(rootPaths));
 }
 
 StorePathsCommand::StorePathsCommand(bool recursive)
     : BuiltPathsCommand(recursive)
 {
 }
 
-void StorePathsCommand::run(ref<Store> store, BuiltPaths && paths)
+void StorePathsCommand::run(ref<Store> store, BuiltPaths && allPaths, BuiltPaths && rootPaths)
 {
     StorePathSet storePaths;
-    for (auto & builtPath : paths)
+    for (auto & builtPath : allPaths)
         for (auto & p : builtPath.outPaths())
             storePaths.insert(p);
 
@@ -245,7 +249,7 @@ MixProfile::MixProfile()
 void MixProfile::updateProfile(const StorePath & storePath)
 {
     if (!profile) return;
-    auto store = getStore().dynamic_pointer_cast<LocalFSStore>();
+    auto store = getDstStore().dynamic_pointer_cast<LocalFSStore>();
     if (!store) throw Error("'--profile' is not supported for this Nix store");
     auto profile2 = absPath(*profile);
     switchLink(profile2,
@@ -308,7 +312,8 @@ MixEnvironment::MixEnvironment() : ignoreEnvironment(false)
     });
 }
 
-void MixEnvironment::setEnviron() {
+void MixEnvironment::setEnviron()
+{
     if (ignoreEnvironment) {
         if (!unset.empty())
             throw UsageError("--unset does not make sense with --ignore-environment");

src/libcmd/command.hh

@@ -45,7 +45,20 @@ struct StoreCommand : virtual Command
 {
     StoreCommand();
     void run() override;
+
+    /**
+     * Return the default Nix store.
+     */
     ref<Store> getStore();
+
+    /**
+     * Return the destination Nix store.
+     */
+    virtual ref<Store> getDstStore()
+    {
+        return getStore();
+    }
+
     virtual ref<Store> createStore();
     /**
      * Main entry point, with a `Store` provided
@@ -68,7 +81,7 @@ struct CopyCommand : virtual StoreCommand
 
     ref<Store> createStore() override;
 
-    ref<Store> getDstStore();
+    ref<Store> getDstStore() override;
 };
 
 /**
@@ -238,7 +251,7 @@ public:
 
     BuiltPathsCommand(bool recursive = false);
 
-    virtual void run(ref<Store> store, BuiltPaths && paths) = 0;
+    virtual void run(ref<Store> store, BuiltPaths && allPaths, BuiltPaths && rootPaths) = 0;
 
     void run(ref<Store> store, Installables && installables) override;
 
@@ -251,7 +264,7 @@ struct StorePathsCommand : public BuiltPathsCommand
 
     virtual void run(ref<Store> store, StorePaths && storePaths) = 0;
 
-    void run(ref<Store> store, BuiltPaths && paths) override;
+    void run(ref<Store> store, BuiltPaths && allPaths, BuiltPaths && rootPaths) override;
 };
 
 /**

src/nix/copy.cc

@@ -4,7 +4,7 @@
 
 using namespace nix;
 
-struct CmdCopy : virtual CopyCommand, virtual BuiltPathsCommand
+struct CmdCopy : virtual CopyCommand, virtual BuiltPathsCommand, MixProfile
 {
     CheckSigsFlag checkSigs = CheckSigs;
 
@@ -43,19 +43,21 @@ struct CmdCopy : virtual CopyCommand, virtual BuiltPathsCommand
 
     Category category() override { return catSecondary; }
 
-    void run(ref<Store> srcStore, BuiltPaths && paths) override
+    void run(ref<Store> srcStore, BuiltPaths && allPaths, BuiltPaths && rootPaths) override
     {
         auto dstStore = getDstStore();
 
         RealisedPath::Set stuffToCopy;
 
-        for (auto & builtPath : paths) {
+        for (auto & builtPath : allPaths) {
             auto theseRealisations = builtPath.toRealisedPaths(*srcStore);
             stuffToCopy.insert(theseRealisations.begin(), theseRealisations.end());
         }
 
         copyPaths(
             *srcStore, *dstStore, stuffToCopy, NoRepair, checkSigs, substitute);
+
+        updateProfile(rootPaths);
     }
 };
 

src/nix/copy.md

@@ -55,6 +55,15 @@ R""(
   # nix copy --to /tmp/nix nixpkgs#hello --no-check-sigs
   ```
 
+* Update the NixOS system profile to point to a closure copied from a
+  remote machine:
+
+  ```console
+  # nix copy --from ssh://server \
+      --profile /nix/var/nix/profiles/system \
+      /nix/store/r14v3km89zm3prwsa521fab5kgzvfbw4-nixos-system-foobar-24.05.20240925.759537f
+  ```
+
 # Description
 
 `nix copy` copies store path closures between two Nix stores. The

src/nix/realisation.cc

@@ -36,7 +36,7 @@ struct CmdRealisationInfo : BuiltPathsCommand, MixJSON
 
     Category category() override { return catSecondary; }
 
-    void run(ref<Store> store, BuiltPaths && paths) override
+    void run(ref<Store> store, BuiltPaths && paths, BuiltPaths && rootPaths) override
     {
         experimentalFeatureSettings.require(Xp::CaDerivations);
         RealisedPath::Set realisations;

tests/functional/zstd.sh

@@ -18,7 +18,9 @@ HASH=$(nix hash path $outPath)
 clearStore
 clearCacheCache
 
-nix copy --from $cacheURI $outPath --no-check-sigs
+nix copy --from $cacheURI $outPath --no-check-sigs --profile $TEST_ROOT/profile
+
+[[ -e $TEST_ROOT/profile ]]
 
 if ls $cacheDir/nar/*.zst &> /dev/null; then
     echo "files do exist"