context: copy symlinks as symlinks and improve error messages

src/pull.rs

@@ -1,5 +1,6 @@
 use std::cmp::min;
 use std::error::Error;
+use std::os::unix::fs::symlink;
 use std::path::Path;
 use std::path::PathBuf;
 
@@ -101,7 +102,13 @@ fn copy_dir_all(src: &Path, dst: &Path) -> Result<(), Box<dyn Error>> {
         let src_path = entry.path();
         let dst_path = dst.join(entry.file_name());
 
-        if src_path.is_dir() {
+        // Reproduce symlinks as symlinks rather than following them, so that
+        // dangling/absolute symlinks do not abort the copy.
+        if std::fs::symlink_metadata(&src_path)?.file_type().is_symlink() {
+            let target = std::fs::read_link(&src_path)?;
+            let _ = std::fs::remove_file(&dst_path);
+            symlink(&target, &dst_path)?;
+        } else if src_path.is_dir() {
             copy_dir_all(&src_path, &dst_path)?;
         } else {
             std::fs::copy(&src_path, &dst_path)?;
@@ -183,12 +190,25 @@ fn checkout_pristine_tar(package_dir: &Path, filename: &str) -> Result<(), Box<d
         .current_dir(package_dir)
         .args(["checkout", format!("../{filename}").as_str()])
         .output()
-        .expect("pristine-tar checkout failed");
+        .map_err(|e| {
+            format!(
+                "Failed to run 'pristine-tar' to check out '{filename}': {}. \
+                 Is 'pristine-tar' installed? It is required to reconstruct \
+                 the upstream orig tarball from a git repository.",
+                e
+            )
+        })?;
 
     if !output.status.success() {
+        let stderr = String::from_utf8_lossy(&output.stderr);
         return Err(format!(
-            "pristine-tar checkout failed with status: {}",
-            output.status
+            "pristine-tar checkout of '{filename}' failed with status: {}.{}",
+            output.status,
+            if stderr.trim().is_empty() {
+                String::new()
+            } else {
+                format!("\npristine-tar output:\n{}", stderr.trim())
+            }
         )
         .into());
     }