closePR: add celebratory message (gitgitgadget#2179)

This looks almost sad for a celebratory event:
git/git#2138 (comment)

Author: webstech

lib/ci-helper.ts

@@ -647,7 +647,7 @@ export class CIHelper {
             }
         }
 
-        let closePR: string | undefined;
+        let upstreamMergeCommit: string | undefined;
         const prLabelsToAdd: string[] = [];
         for (const branch of this.config.repo.trackingBranches) {
             const mergeCommit = await this.identifyMergeCommit(branch, tipCommitInGitGit);
@@ -656,7 +656,7 @@ export class CIHelper {
             }
 
             if (this.config.repo.closingBranches.includes(branch)) {
-                closePR = mergeCommit;
+                upstreamMergeCommit = mergeCommit;
             }
 
             if (!prMeta.mergedIntoUpstream) {
@@ -683,7 +683,7 @@ export class CIHelper {
         }
 
         let optionsUpdated = false;
-        if (closePR) {
+        if (upstreamMergeCommit) {
             if (options.openPRs) {
                 delete options.openPRs[pullRequestURL];
                 optionsUpdated = true;
@@ -697,7 +697,7 @@ export class CIHelper {
                 optionsUpdated = true;
             }
 
-            await this.github.closePR(prKey, closePR);
+            await this.github.closePRAsMerged(prKey, upstreamMergeCommit);
         }
 
         if (notesUpdated) {

lib/github-glue.ts

@@ -289,7 +289,7 @@ export class GitHubGlue {
         return result.data.map((res: { id: number }) => `${res.id}`);
     }
 
-    public async closePR(pullRequest: pullRequestKeyInfo, viaMergeCommit: string): Promise<number> {
+    public async closePRAsMerged(pullRequest: pullRequestKeyInfo, mergeCommit: string): Promise<number> {
         const prKey = getPullRequestKey(pullRequest);
 
         await this.ensureAuthenticated(prKey.owner);
@@ -298,8 +298,16 @@ export class GitHubGlue {
             ...prKey,
         });
 
+        const body =
+            "Congratulations! 🎉 Your patch series was merged" +
+            ` into upstream via ${mergeCommit}.\n\n` +
+            "Note: this pull request will show as" +
+            ' "Closed" rather than "Merged" because the' +
+            " merge happened in the upstream repository," +
+            " not on GitHub. This is expected —" +
+            " your contribution has been accepted!";
         const result = await this.client.rest.issues.createComment({
-            body: `Closed via ${viaMergeCommit}.`,
+            body,
             issue_number: prKey.pull_number,
             owner: prKey.owner,
             repo: prKey.repo,

tests/github-glue.test.ts

@@ -99,7 +99,7 @@ test("pull requests", async () => {
             });
 
             if (pullRequestURL.length) {
-                await github.closePR(pullRequestURL, "Not merged");
+                await github.closePRAsMerged(pullRequestURL, "Not merged");
             }
 
             try {
@@ -212,7 +212,7 @@ test("pull requests", async () => {
 
         await github.addPRLabels(prData.html_url, ["bug"]);
 
-        const cNumber = await github.closePR(prData.html_url, "Not merged");
+        const cNumber = await github.closePRAsMerged(prData.html_url, "Not merged");
         expect(cNumber).toBeGreaterThan(id);
 
         // delete local and remote branches