Add 'nix store delete' command

src/nix/store-delete.cc

@@ -0,0 +1,45 @@
+#include "command.hh"
+#include "common-args.hh"
+#include "shared.hh"
+#include "store-api.hh"
+
+using namespace nix;
+
+struct CmdStoreDelete : StorePathsCommand
+{
+    GCOptions options { .action = GCOptions::gcDeleteSpecific };
+
+    CmdStoreDelete()
+    {
+        addFlag({
+            .longName = "ignore-liveness",
+            .description = "do not check whether the paths are reachable from a root",
+            .handler = {&options.ignoreLiveness, true}
+        });
+    }
+
+    std::string description() override
+    {
+        return "delete paths from the Nix store";
+    }
+
+    std::string doc() override
+    {
+        return
+          #include "store-delete.md"
+          ;
+    }
+
+    void run(ref<Store> store, std::vector<StorePath> storePaths) override
+    {
+
+        for (auto & path : storePaths)
+            options.pathsToDelete.insert(path);
+
+        GCResults results;
+        PrintFreed freed(true, results);
+        store->collectGarbage(options, results);
+    }
+};
+
+static auto rCmdStoreDelete = registerCommand2<CmdStoreDelete>({"store", "delete"});

src/nix/store-delete.md

@@ -0,0 +1,24 @@
+R""(
+
+# Examples
+
+* Delete a specific store path:
+
+  ```console
+  # nix store delete /nix/store/yb5q57zxv6hgqql42d5r8b5k5mcq6kay-hello-2.10
+  ```
+
+# Description
+
+This command deletes the store paths specified by *installables*. ,
+but only if it is safe to do so; that is, when the path is not
+reachable from a root of the garbage collector. This means that you
+can only delete paths that would also be deleted by `nix store
+gc`. Thus, `nix store delete` is a more targeted version of `nix store
+gc`.
+
+With the option `--ignore-liveness`, reachability from the roots is
+ignored. However, the path still won't be deleted if there are other
+paths in the store that refer to it (i.e., depend on it).
+
+)""