Add command 'nix profile diff-closure'

This shows all changes between generations of a profile. E.g.

  $ nix profile diff-closures --profile /nix/var/nix/profiles/system
  Generation 654 -> 655:
    nix: 2.4pre20200617_5d69bbf → 2.4pre20200701_6ff9aa8, +42.2 KiB

  Generation 655 -> 656:
    blender-bin: 2.83.0 → 2.83.1, -294.2 KiB

  Generation 656 -> 657:
    curl: 7.68.0 → 7.70.0, +19.1 KiB
    firmware-linux-nonfree: 2020-01-22 → 2020-05-19, +30827.7 KiB
    ibus: -21.8 KiB
    initrd-linux: 5.4.46 → 5.4.49
    ...

src/nix/command.hh

@@ -244,4 +244,10 @@ void completeFlakeRefWithFragment(
     const Strings & defaultFlakeAttrPaths,
     std::string_view prefix);
 
+void printClosureDiff(
+    ref<Store> store,
+    const StorePath & beforePath,
+    const StorePath & afterPath,
+    std::string_view indent);
+
 }

src/nix/diff-closures.cc

@@ -6,7 +6,7 @@
 
 #include <regex>
 
-using namespace nix;
+namespace nix {
 
 struct Info
 {
@@ -52,40 +52,12 @@ std::string showVersions(const std::set<std::string> & versions)
     return concatStringsSep(", ", versions2);
 }
 
-struct CmdDiffClosures : SourceExprCommand
+void printClosureDiff(
+    ref<Store> store,
+    const StorePath & beforePath,
+    const StorePath & afterPath,
+    std::string_view indent)
 {
-    std::string _before, _after;
-
-    CmdDiffClosures()
-    {
-        expectArg("before", &_before);
-        expectArg("after", &_after);
-    }
-
-    std::string description() override
-    {
-        return "show what packages and versions were added and removed between two closures";
-    }
-
-    Category category() override { return catSecondary; }
-
-    Examples examples() override
-    {
-        return {
-            {
-                "To show what got added and removed between two versions of the NixOS system profile:",
-                "nix diff-closures /nix/var/nix/profiles/system-655-link /nix/var/nix/profiles/system-658-link",
-            },
-        };
-    }
-
-    void run(ref<Store> store) override
-    {
-        auto before = parseInstallable(store, _before);
-        auto beforePath = toStorePath(store, Realise::Outputs, operateOn, before);
-        auto after = parseInstallable(store, _after);
-        auto afterPath = toStorePath(store, Realise::Outputs, operateOn, after);
-
     auto beforeClosure = getClosureInfo(store, beforePath);
     auto afterClosure = getClosureInfo(store, afterPath);
 
@@ -125,10 +97,50 @@ struct CmdDiffClosures : SourceExprCommand
                 items.push_back(fmt("%s → %s", showVersions(removed), showVersions(added)));
             if (showDelta)
                 items.push_back(fmt("%s%+.1f KiB" ANSI_NORMAL, sizeDelta > 0 ? ANSI_RED : ANSI_GREEN, sizeDelta / 1024.0));
-                std::cout << fmt("%s: %s\n", name, concatStringsSep(", ", items));
+            std::cout << fmt("%s%s: %s\n", indent, name, concatStringsSep(", ", items));
         }
     }
 }
+
+}
+
+using namespace nix;
+
+struct CmdDiffClosures : SourceExprCommand
+{
+    std::string _before, _after;
+
+    CmdDiffClosures()
+    {
+        expectArg("before", &_before);
+        expectArg("after", &_after);
+    }
+
+    std::string description() override
+    {
+        return "show what packages and versions were added and removed between two closures";
+    }
+
+    Category category() override { return catSecondary; }
+
+    Examples examples() override
+    {
+        return {
+            {
+                "To show what got added and removed between two versions of the NixOS system profile:",
+                "nix diff-closures /nix/var/nix/profiles/system-655-link /nix/var/nix/profiles/system-658-link",
+            },
+        };
+    }
+
+    void run(ref<Store> store) override
+    {
+        auto before = parseInstallable(store, _before);
+        auto beforePath = toStorePath(store, Realise::Outputs, operateOn, before);
+        auto after = parseInstallable(store, _after);
+        auto afterPath = toStorePath(store, Realise::Outputs, operateOn, after);
+        printClosureDiff(store, beforePath, afterPath, "");
+    }
 };
 
 static auto r1 = registerCommand<CmdDiffClosures>("diff-closures");

src/nix/profile.cc

@@ -7,6 +7,7 @@
 #include "builtins/buildenv.hh"
 #include "flake/flakeref.hh"
 #include "../nix-env/user-env.hh"
+#include "profiles.hh"
 
 #include <nlohmann/json.hpp>
 #include <regex>
@@ -394,6 +395,46 @@ struct CmdProfileInfo : virtual EvalCommand, virtual StoreCommand, MixDefaultPro
     }
 };
 
+struct CmdProfileDiffClosures : virtual EvalCommand, virtual StoreCommand, MixDefaultProfile
+{
+    std::string description() override
+    {
+        return "show the closure difference between each generation of a profile";
+    }
+
+    Examples examples() override
+    {
+        return {
+            Example{
+                "To show what changed between each generation of the NixOS system profile:",
+                "nix profile diff-closure --profile /nix/var/nix/profiles/system"
+            },
+        };
+    }
+
+    void run(ref<Store> store) override
+    {
+        auto [gens, curGen] = findGenerations(*profile);
+
+        std::optional<Generation> prevGen;
+        bool first = true;
+
+        for (auto & gen : gens) {
+            if (prevGen) {
+                if (!first) std::cout << "\n";
+                first = false;
+                std::cout << fmt("Generation %d -> %d:\n", prevGen->number, gen.number);
+                printClosureDiff(store,
+                    store->followLinksToStorePath(prevGen->path),
+                    store->followLinksToStorePath(gen.path),
+                    "  ");
+            }
+
+            prevGen = gen;
+        }
+    }
+};
+
 struct CmdProfile : virtual MultiCommand, virtual Command
 {
     CmdProfile()
@@ -402,6 +443,7 @@ struct CmdProfile : virtual MultiCommand, virtual Command
               {"remove", []() { return make_ref<CmdProfileRemove>(); }},
               {"upgrade", []() { return make_ref<CmdProfileUpgrade>(); }},
               {"info", []() { return make_ref<CmdProfileInfo>(); }},
+              {"diff-closures", []() { return make_ref<CmdProfileDiffClosures>(); }},
           })
     { }
 
@@ -425,4 +467,3 @@ struct CmdProfile : virtual MultiCommand, virtual Command
 };
 
 static auto r1 = registerCommand<CmdProfile>("profile");
-