deb: retrieve .deb artifacts

sbuild options: unshare, build directory

context: retrieve files

src/context/api.rs

@@ -18,6 +18,8 @@ pub trait CommandRunner {
 
 pub trait ContextDriver {
     fn ensure_available(&self, src: &Path, dest_root: &str) -> io::Result<PathBuf>;
+    fn retrieve_path(&self, src: &Path, dest: &Path) -> io::Result<()>;
+    fn list_files(&self, path: &Path) -> io::Result<Vec<PathBuf>>;
     fn create_runner(&self, program: String) -> Box<dyn CommandRunner>;
     fn prepare_work_dir(&self) -> io::Result<String>;
 }
@@ -60,6 +62,19 @@ impl Context {
         self.driver().prepare_work_dir()
     }
 
+    /// Retrieve a file or directory from the context to the local filesystem.
+    ///
+    /// The `src` path is on the context, `dest` is on the local machine.
+    /// If `src` is a directory, it is copied recursively.
+    pub fn retrieve_path(&self, src: &Path, dest: &Path) -> io::Result<()> {
+        self.driver().retrieve_path(src, dest)
+    }
+
+    /// List files in a directory on the context.
+    pub fn list_files(&self, path: &Path) -> io::Result<Vec<PathBuf>> {
+        self.driver().list_files(path)
+    }
+
     fn driver(&self) -> Box<dyn ContextDriver> {
         match self {
             Context::Local => Box::new(LocalDriver),