context: copy symlinks as symlinks and improve error messages

src/context/local.rs

@@ -2,6 +2,7 @@
 /// Context driver: Does nothing
 use super::api::ContextDriver;
 use std::io;
+use std::os::unix::fs::symlink;
 use std::path::{Path, PathBuf};
 use std::process::Command;
 use std::time::SystemTime;
@@ -112,6 +113,14 @@ impl ContextDriver for LocalDriver {
 }
 
 fn copy_dir_recursive(src: &Path, dest: &Path) -> io::Result<()> {
+    // Reproduce symlinks as symlinks rather than following them, so that
+    // dangling/absolute symlinks do not abort the copy.
+    if std::fs::symlink_metadata(src)?.file_type().is_symlink() {
+        let target = std::fs::read_link(src)?;
+        let _ = std::fs::remove_file(dest);
+        return symlink(&target, dest);
+    }
+
     if src.is_dir() {
         std::fs::create_dir_all(dest)?;
         for entry in std::fs::read_dir(src)? {