feat: add option for nix-env arguments (#555)

config.example.toml

@@ -112,6 +112,7 @@
 #suse_dup = false
 #rpm_ostree = false
 #nix_arguments = "--flake"
+#nix_env_arguments = "--prebuilt-only"
 
 [git]
 #max_concurrency = 5

src/config.rs

@@ -341,6 +341,9 @@ pub struct Linux {
     #[merge(strategy = crate::utils::merge_strategies::string_append_opt)]
     nix_arguments: Option<String>,
 
+    #[merge(strategy = crate::utils::merge_strategies::string_append_opt)]
+    nix_env_arguments: Option<String>,
+
     #[merge(strategy = crate::utils::merge_strategies::string_append_opt)]
     apt_arguments: Option<String>,
 
@@ -1275,6 +1278,14 @@ impl Config {
             .and_then(|linux| linux.nix_arguments.as_deref())
     }
 
+    /// Extra nix-env arguments
+    pub fn nix_env_arguments(&self) -> Option<&str> {
+        self.config_file
+            .linux
+            .as_ref()
+            .and_then(|linux| linux.nix_env_arguments.as_deref())
+    }
+
     /// Extra Home Manager arguments
     pub fn home_manager(&self) -> Option<&Vec<String>> {
         self.config_file

src/steps/os/unix.rs

@@ -423,7 +423,12 @@ pub fn run_nix(ctx: &ExecutionContext) -> Result<()> {
             .arg("--verbose")
             .status_checked()
     } else {
-        run_type.execute(nix_env).arg("--upgrade").status_checked()
+        let mut command = run_type.execute(nix_env);
+        command.arg("--upgrade");
+        if let Some(args) = ctx.config().nix_env_arguments() {
+            command.args(args.split_whitespace());
+        };
+        command.status_checked()
     }
 }