pkgs/rollup: Check if the `--to` directory is actually writable

Otherwise we would create the patches, but fail to apply them. The issue
is that we already moved the tag forward, so the user now needs to
manually create the patches again (after exiting the sandbox).

1 files changed, 24 insertions, 1 deletions

diff --git a/pkgs/by-name/ro/rollup/src/main.rs b/pkgs/by-name/ro/rollup/src/main.rs
index 12cf7dd9..069ed59b 100644
--- a/pkgs/by-name/ro/rollup/src/main.rs
+++ b/pkgs/by-name/ro/rollup/src/main.rs
@@ -2,7 +2,7 @@ use std::{
     env::current_dir,
     fs,
     io::Write,
-    path::PathBuf,
+    path::{Path, PathBuf},
     process::{Command, Stdio},
 };
 
@@ -285,3 +285,26 @@ fn apply_patches(patch_files: Vec<PathBuf>, to: PathBuf, debug_parse: bool) -> R
 
     Ok(())
 }
+
+fn check_to(to: &Path) -> Result<()> {
+    let to = to.join(".git");
+
+    // NOTE: We cannot just try to stat() the path, because landlock might be in use and does not
+    // currently deny that (tracked in: https://github.com/landlock-lsm/linux/issues/52) <2026-11-09>
+    // So we instead try to list it.
+    let is_listable = {
+        let dir_entries = fs::read_dir(&to).with_context(|| {
+            format!(
+                "Failed check regarding `--to` directory (`{}`) readability. Are you in a sandbox?",
+                to.display()
+            )
+        })?;
+        dir_entries.count() > 0
+    };
+
+    if !is_listable {
+        bail!("To directory (`{}`) is not readable", to.display());
+    }
+
+    Ok(())
+}