Remove static initializers for `RegisterLegacyCommand`

This moves the "legacy"/"nix2" commands under a new `src/legacy/`
directory, instead of being scattered around in a bunch of different
directories.

A new `liblegacy` build target is defined, and the `nix` binary is
linked against it.

Then, `RegisterLegacyCommand` is replaced with `LegacyCommand::add`
calls in functions like `registerNixCollectGarbage()`. These
registration functions are called explicitly in `src/nix/main.cc`.

See: https://git.lix.systems/lix-project/lix/issues/359

Change-Id: Id450ffc3f793374907599cfcc121863b792aac1a

1 files changed, 7 insertions, 2 deletions

diff --git a/src/nix/prefetch.cc b/src/nix/prefetch.cc
index b99cd5dd0..0183b0008 100644
--- a/src/nix/prefetch.cc
+++ b/src/nix/prefetch.cc
@@ -9,10 +9,11 @@
 #include "eval-inline.hh" // IWYU pragma: keep
 #include "legacy.hh"
 #include "terminal.hh"
+#include "prefetch-command.hh"
 
 #include <nlohmann/json.hpp>
 
-using namespace nix;
+namespace nix {
 
 /* If ‘url’ starts with ‘mirror://’, then resolve it using the list of
    mirrors defined in Nixpkgs. */
@@ -248,7 +249,9 @@ static int main_nix_prefetch_url(int argc, char * * argv)
     }
 }
 
-static RegisterLegacyCommand r_nix_prefetch_url("nix-prefetch-url", main_nix_prefetch_url);
+void registerNixPrefetchUrl() {
+    LegacyCommands::add("nix-prefetch-url", main_nix_prefetch_url);
+}
 
 struct CmdStorePrefetchFile : StoreCommand, MixJSON
 {
@@ -328,3 +331,5 @@ struct CmdStorePrefetchFile : StoreCommand, MixJSON
 };
 
 static auto rCmdStorePrefetchFile = registerCommand2<CmdStorePrefetchFile>({"store", "prefetch-file"});
+
+}