Add Co-authored-by trailers to Merge's squash commit

web/src/task.ts

@@ -1,4 +1,4 @@
-import { get, post, type ByreEvent, type Snapshot } from "./api.js";
+import { get, post, type ByreEvent, type Participant, type Snapshot } from "./api.js";
 import { ago, errorText, h, replace, showAlert, showConfirm } from "./dom.js";
 import { markdown } from "./markdown.js";
 import { openChanges } from "./panes.js";
@@ -161,10 +161,18 @@ export function mountTranscript(root: HTMLElement): () => void {
       { disabled: busy || unmerged?.taskId !== task.id || !unmerged.has, title: `The agent merges ${target} in, then byre squashes into one commit on ${target} and pushes it to origin` },
       "Merge",
     );
-    merge.onclick = () =>
-      confirmThen(`Merge "${task.title}" into ${target}?`, "Merge", false, async () => {
+    merge.onclick = async () => {
+      let coAuthors;
+      try {
+        coAuthors = await get("/api/tasks/{taskId}/co-authors", { path: { taskId: task.id } });
+      } catch (err) {
+        void showAlert(errorText(err));
+        return;
+      }
+      await confirmThen(mergeQuestion(task.merge_title, target, coAuthors), "Merge", false, async () => {
         await post("/api/tasks/{taskId}/merge", { path: { taskId: task.id } });
       });
+    };
     const mergeIn = h("button", { disabled: busy, title: `Ask the agent to bring ${target} into this branch and resolve any conflicts` }, `Sync from ${target}`);
     mergeIn.onclick = async () => {
       mergeIn.disabled = true;
@@ -881,6 +889,19 @@ function messageImages(ids: unknown): HTMLElement | null {
   );
 }
 
+function mergeQuestion(title: string, target: string, coAuthors: Participant[]): string {
+  const lines = [`Merge "${title}" into ${target}?`];
+  const credited = coAuthors.filter((p) => p.git_name && p.git_email);
+  const missing = coAuthors.filter((p) => !p.git_name || !p.git_email);
+  if (credited.length > 0) {
+    lines.push("", "Co-authored-by:", ...credited.map((p) => `  ${p.git_name} <${p.git_email}>`));
+  }
+  if (missing.length > 0) {
+    lines.push("", "No git identity, so no trailer:", ...missing.map((p) => `  ${p.display_name} (${p.login})`));
+  }
+  return lines.join("\n");
+}
+
 async function confirmThen(question: string, action: string, danger: boolean, act: () => Promise<void>) {
   if (!(await showConfirm(question, action, danger))) {
     return;