Factor out --from / --to logic

src/libcmd/command.cc

@@ -73,13 +73,16 @@ ref<Store> EvalCommand::getEvalStore()
 
 ref<EvalState> EvalCommand::getEvalState()
 {
-    if (!evalState) evalState =
-#if HAVE_BOEHMGC
-        std::allocate_shared<EvalState>(traceable_allocator<EvalState>(),
-#else
-        std::make_shared<EvalState>(
-#endif
-            searchPath, getEvalStore(), getStore());
+    if (!evalState)
+        evalState =
+            #if HAVE_BOEHMGC
+            std::allocate_shared<EvalState>(traceable_allocator<EvalState>(),
+                searchPath, getEvalStore(), getStore())
+            #else
+            std::make_shared<EvalState>(
+                searchPath, getEvalStore(), getStore())
+            #endif
+            ;
     return ref<EvalState>(evalState);
 }
 
@@ -156,6 +159,43 @@ void StorePathsCommand::run(ref<Store> store, BuiltPaths && paths)
     run(store, std::move(sorted));
 }
 
+CopyCommand::CopyCommand()
+    : BuiltPathsCommand(true)
+{
+    addFlag({
+        .longName = "from",
+        .description = "URL of the source Nix store.",
+        .labels = {"store-uri"},
+        .handler = {&srcUri},
+    });
+
+    addFlag({
+        .longName = "to",
+        .description = "URL of the destination Nix store.",
+        .labels = {"store-uri"},
+        .handler = {&dstUri},
+    });
+}
+
+ref<Store> CopyCommand::createStore()
+{
+    return srcUri.empty() ? StoreCommand::createStore() : openStore(srcUri);
+}
+
+void CopyCommand::run(ref<Store> store)
+{
+    if (srcUri.empty() && dstUri.empty())
+        throw UsageError("you must pass '--from' and/or '--to'");
+
+    BuiltPathsCommand::run(store);
+}
+
+void CopyCommand::run(ref<Store> srcStore, BuiltPaths && paths)
+{
+    ref<Store> dstStore = dstUri.empty() ? openStore() : openStore(dstUri);
+    run(srcStore, dstStore, std::move(paths));
+}
+
 void StorePathCommand::run(ref<Store> store, std::vector<StorePath> && storePaths)
 {
     if (storePaths.size() != 1)

src/libcmd/command.hh

@@ -176,6 +176,23 @@ public:
     bool useDefaultInstallables() override { return !all; }
 };
 
+/* A command that copies something between `--from` and `--to`
+   stores. */
+struct CopyCommand : virtual BuiltPathsCommand
+{
+    std::string srcUri, dstUri;
+
+    CopyCommand();
+
+    ref<Store> createStore() override;
+
+    void run(ref<Store> store) override;
+
+    void run(ref<Store> srcStore, BuiltPaths && paths) override;
+
+    virtual void run(ref<Store> srcStore, ref<Store> dstStore, BuiltPaths && paths) = 0;
+};
+
 struct StorePathsCommand : public BuiltPathsCommand
 {
     StorePathsCommand(bool recursive = false);

src/nix/copy.cc

@@ -1,17 +1,11 @@
 #include "command.hh"
 #include "shared.hh"
 #include "store-api.hh"
-#include "sync.hh"
-#include "thread-pool.hh"
-
-#include <atomic>
 
 using namespace nix;
 
-struct CmdCopy : BuiltPathsCommand
+struct CmdCopy : CopyCommand
 {
-    std::string srcUri, dstUri;
-
     CheckSigsFlag checkSigs = CheckSigs;
 
     SubstituteFlag substitute = NoSubstitute;
@@ -21,20 +15,6 @@ struct CmdCopy : BuiltPathsCommand
     CmdCopy()
         : BuiltPathsCommand(true)
     {
-        addFlag({
-            .longName = "from",
-            .description = "URL of the source Nix store.",
-            .labels = {"store-uri"},
-            .handler = {&srcUri},
-        });
-
-        addFlag({
-            .longName = "to",
-            .description = "URL of the destination Nix store.",
-            .labels = {"store-uri"},
-            .handler = {&dstUri},
-        });
-
         addFlag({
             .longName = "no-check-sigs",
             .description = "Do not require that paths are signed by trusted keys.",
@@ -65,23 +45,8 @@ struct CmdCopy : BuiltPathsCommand
 
     Category category() override { return catSecondary; }
 
-    ref<Store> createStore() override
+    void run(ref<Store> srcStore, ref<Store> dstStore, BuiltPaths && paths) override
     {
-        return srcUri.empty() ? StoreCommand::createStore() : openStore(srcUri);
-    }
-
-    void run(ref<Store> store) override
-    {
-        if (srcUri.empty() && dstUri.empty())
-            throw UsageError("you must pass '--from' and/or '--to'");
-
-        BuiltPathsCommand::run(store);
-    }
-
-    void run(ref<Store> srcStore, BuiltPaths && paths) override
-    {
-        ref<Store> dstStore = dstUri.empty() ? openStore() : openStore(dstUri);
-
         RealisedPath::Set stuffToCopy;
 
         for (auto & builtPath : paths) {