sed: separate lines with NUL when -z is given

src/sed/command.rs

@@ -79,6 +79,13 @@ pub struct ProcessingContext {
     pub append_elements: Vec<AppendElement>,
 }
 
+impl ProcessingContext {
+    /// Return the byte that separates lines: \0 with -z, otherwise \n.
+    pub fn line_separator(&self) -> u8 {
+        if self.null_data { b'\0' } else { b'\n' }
+    }
+}
+
 #[derive(Clone, Debug)]
 /// Elements that shall be appended at the end of each command processing cycle
 pub enum AppendElement {
@@ -394,6 +401,8 @@ pub struct InputAction {
     pub next_command: Option<Rc<RefCell<Command>>>,
     /// Data to prepend to the read contents
     pub prepend: Vec<u8>,
+    /// True if the prepended line ended with a line separator
+    pub prepend_terminated: bool,
 }
 
 #[cfg(test)]

src/sed/compiler.rs

@@ -1143,10 +1143,11 @@ fn compile_read_line_command(
     let path = read_file_path(lines, line)?;
     // Reuse a reader keyed by path so all `R` commands on the same file share
     // one cursor (see `ProcessingContext::named_readers`).
+    let separator = context.line_separator();
     let reader = context
         .named_readers
         .entry(path.clone())
-        .or_insert_with(|| NamedReader::new(path))
+        .or_insert_with(|| NamedReader::new(path, separator))
         .clone();
     cmd.data = CommandData::NamedReader(reader);
     Ok(CommandHandling::Continue)