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
    ...

1 files changed, 6 insertions, 0 deletions

diff --git a/src/nix/command.hh b/src/nix/command.hh
index 1c7413300..856721ebf 100644
--- a/src/nix/command.hh
+++ b/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);
+
 }