Add --out-link flag

Closes #137

src/home.rs

@@ -34,11 +34,15 @@ impl NHRunnable for HomeArgs {
 
 impl HomeRebuildArgs {
     fn rebuild(&self, action: &HomeSubcommand) -> Result<()> {
-        let out_dir = tempfile::Builder::new().prefix("nh-home-").tempdir()?;
-        let out_link = out_dir.path().join("result");
-        let out_link_str = out_link.to_str().unwrap();
-        debug!("out_dir: {:?}", out_dir);
-        debug!("out_link {:?}", out_link);
+        let out_path: Box<dyn crate::util::MaybeTempPath> = match self.common.out_link {
+            Some(ref p) => Box::new(p.clone()),
+            None => Box::new({
+                let dir = tempfile::Builder::new().prefix("nh-home").tempdir()?;
+                (dir.as_ref().join("result"), dir)
+            }),
+        };
+
+        debug!(?out_path);
 
         let username = std::env::var("USER").expect("Couldn't get username");
 
@@ -91,7 +95,8 @@ impl HomeRebuildArgs {
 
         commands::BuildCommandBuilder::default()
             .flakeref(&flakeref)
-            .extra_args(["--out-link", out_link_str])
+            .extra_args(["--out-link"])
+            .extra_args([out_path.get_path()])
             .extra_args(&self.extra_args)
             .message("Building home configuration")
             .nom(!self.common.no_nom)
@@ -115,7 +120,8 @@ impl HomeRebuildArgs {
         if let Some(prev_gen) = prev_generation {
             commands::CommandBuilder::default()
                 .args(self.common.diff_provider.split_ascii_whitespace())
-                .args([(prev_gen.to_str().unwrap()), out_link_str])
+                .args([(prev_gen.to_str().unwrap())])
+                .args([out_path.get_path()])
                 .message("Comparing changes")
                 .build()?
                 .exec()?;
@@ -140,13 +146,13 @@ impl HomeRebuildArgs {
         }
 
         commands::CommandBuilder::default()
-            .args([&format!("{}/activate", out_link_str)])
+            .args([out_path.get_path().join("activate")])
             .message("Activating configuration")
             .build()?
             .exec()?;
 
         // Drop the out dir *only* when we are finished
-        drop(out_dir);
+        drop(out_path);
 
         Ok(())
     }

src/interface.rs

@@ -146,6 +146,10 @@ pub struct CommonRebuildArgs {
         default_value = "nvd diff"
     )]
     pub diff_provider: String,
+
+    /// Path to save the result link. Defaults to using a temporary directory.
+    #[arg(long, short)]
+    pub out_link: Option<PathBuf>
 }
 
 #[derive(Args, Debug)]

src/nixos.rs

@@ -36,11 +36,15 @@ impl OsRebuildArgs {
             None => hostname::get().context("Failed to get hostname")?,
         };
 
-        let out_dir = tempfile::Builder::new().prefix("nh-os-").tempdir()?;
-        let out_link = out_dir.path().join("result");
-        let out_link_str = out_link.to_str().unwrap();
-        debug!("out_dir: {:?}", out_dir);
-        debug!("out_link {:?}", out_link);
+        let out_path: Box<dyn crate::util::MaybeTempPath> = match self.common.out_link {
+            Some(ref p) => Box::new(p.clone()),
+            None => Box::new({
+                let dir = tempfile::Builder::new().prefix("nh-os").tempdir()?;
+                (dir.as_ref().join("result"), dir)
+            }),
+        };
+
+        debug!(?out_path);
 
         let flake_output = format!(
             "{}#nixosConfigurations.\"{:?}\".config.system.build.toplevel",
@@ -79,7 +83,8 @@ impl OsRebuildArgs {
         commands::BuildCommandBuilder::default()
             .flakeref(flake_output)
             .message("Building NixOS configuration")
-            .extra_args(["--out-link", out_link_str])
+            .extra_args(["--out-link"])
+            .extra_args([out_path.get_path()])
             .extra_args(&self.extra_args)
             .nom(!self.common.no_nom)
             .build()?
@@ -96,8 +101,8 @@ impl OsRebuildArgs {
         debug!("target_specialisation: {target_specialisation:?}");
 
         let target_profile = match &target_specialisation {
-            None => out_link.to_owned(),
-            Some(spec) => out_link.join("specialisation").join(spec),
+            None => out_path.get_path().to_owned(),
+            Some(spec) => out_path.get_path().join("specialisation").join(spec),
         };
 
         target_profile.try_exists().context("Doesn't exist")?;
@@ -143,13 +148,16 @@ impl OsRebuildArgs {
                     "--profile",
                     SYSTEM_PROFILE,
                     "--set",
-                    out_link_str,
                 ])
+                .args([out_path.get_path()])
                 .build()?
                 .exec()?;
 
             // !! Use the base profile aka no spec-namespace
-            let switch_to_configuration = out_link.join("bin").join("switch-to-configuration");
+            let switch_to_configuration = out_path
+                .get_path()
+                .join("bin")
+                .join("switch-to-configuration");
             let switch_to_configuration = switch_to_configuration.to_str().unwrap();
 
             commands::CommandBuilder::default()
@@ -160,7 +168,7 @@ impl OsRebuildArgs {
         }
 
         // Drop the out dir *only* when we are finished
-        drop(out_dir);
+        drop(out_path);
 
         Ok(())
     }

src/util.rs

@@ -2,7 +2,9 @@ extern crate semver;
 
 use color_eyre::{eyre, Result};
 use semver::Version;
+use tempfile::TempDir;
 
+use std::path::{Path, PathBuf};
 use std::process::Command;
 use std::str;
 
@@ -56,3 +58,19 @@ pub fn get_nix_version() -> Result<String> {
 
     Err(eyre::eyre!("Failed to extract version"))
 }
+
+pub trait MaybeTempPath: std::fmt::Debug {
+    fn get_path(&self) -> &Path;
+}
+
+impl MaybeTempPath for PathBuf {
+    fn get_path(&self) -> &Path {
+        self.as_ref()
+    }
+}
+
+impl MaybeTempPath for (PathBuf, TempDir) {
+    fn get_path(&self) -> &Path {
+        self.0.as_ref()
+    }
+}