Use prompt-based co-author attribution with config override (#11617)

codex-rs/core/src/commit_attribution.rs

@@ -0,0 +1,76 @@
+const DEFAULT_ATTRIBUTION_VALUE: &str = "Codex <noreply@openai.com>";
+
+fn build_commit_message_trailer(config_attribution: Option<&str>) -> Option<String> {
+    let value = resolve_attribution_value(config_attribution)?;
+    Some(format!("Co-authored-by: {value}"))
+}
+
+pub(crate) fn commit_message_trailer_instruction(
+    config_attribution: Option<&str>,
+) -> Option<String> {
+    let trailer = build_commit_message_trailer(config_attribution)?;
+    Some(format!(
+        "When you write or edit a git commit message, ensure the message ends with this trailer exactly once:\n{trailer}\n\nRules:\n- Keep existing trailers and append this trailer at the end if missing.\n- Do not duplicate this trailer if it already exists.\n- Keep one blank line between the commit body and trailer block."
+    ))
+}
+
+fn resolve_attribution_value(config_attribution: Option<&str>) -> Option<String> {
+    match config_attribution {
+        Some(value) => {
+            let trimmed = value.trim();
+            if trimmed.is_empty() {
+                None
+            } else {
+                Some(trimmed.to_string())
+            }
+        }
+        None => Some(DEFAULT_ATTRIBUTION_VALUE.to_string()),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::build_commit_message_trailer;
+    use super::commit_message_trailer_instruction;
+    use super::resolve_attribution_value;
+
+    #[test]
+    fn blank_attribution_disables_trailer_prompt() {
+        assert_eq!(build_commit_message_trailer(Some("")), None);
+        assert_eq!(commit_message_trailer_instruction(Some("   ")), None);
+    }
+
+    #[test]
+    fn default_attribution_uses_codex_trailer() {
+        assert_eq!(
+            build_commit_message_trailer(None).as_deref(),
+            Some("Co-authored-by: Codex <noreply@openai.com>")
+        );
+    }
+
+    #[test]
+    fn resolve_value_handles_default_custom_and_blank() {
+        assert_eq!(
+            resolve_attribution_value(None),
+            Some("Codex <noreply@openai.com>".to_string())
+        );
+        assert_eq!(
+            resolve_attribution_value(Some("MyAgent <me@example.com>")),
+            Some("MyAgent <me@example.com>".to_string())
+        );
+        assert_eq!(
+            resolve_attribution_value(Some("MyAgent")),
+            Some("MyAgent".to_string())
+        );
+        assert_eq!(resolve_attribution_value(Some("   ")), None);
+    }
+
+    #[test]
+    fn instruction_mentions_trailer_and_omits_generated_with() {
+        let instruction = commit_message_trailer_instruction(Some("AgentX <agent@example.com>"))
+            .expect("instruction expected");
+        assert!(instruction.contains("Co-authored-by: AgentX <agent@example.com>"));
+        assert!(instruction.contains("exactly once"));
+        assert!(!instruction.contains("Generated-with"));
+    }
+}