Add forward-merger code

src/config.ts

@@ -24,6 +24,7 @@ export type OpsBotConfigFeatureNames = {
   label_checker: boolean;
   release_drafter: boolean;
   recently_updated: boolean;
+  forward_merger: boolean;
 };
 
 /**
@@ -49,6 +50,7 @@ export const DefaultOpsBotConfig: OpsBotConfig = {
   release_drafter: false,
   recently_updated: false,
   recently_updated_threshold: 5,
+  forward_merger: false,
 };
 
 /**

src/index.ts

@@ -20,11 +20,13 @@ import { initBranchChecker } from "./plugins/BranchChecker";
 import { initLabelChecker } from "./plugins/LabelChecker";
 import { initRecentlyUpdated } from "./plugins/RecentlyUpdated";
 import { initReleaseDrafter } from "./plugins/ReleaseDrafter";
+import { initForwardMerger } from "./plugins/ForwardMerger";
 
 export = (app: Probot) => {
   initBranchChecker(app);
   initLabelChecker(app);
   initReleaseDrafter(app);
   initAutoMerger(app);
   initRecentlyUpdated(app);
+  initForwardMerger(app);
 };

src/plugins/ForwardMerger/forward_merger.ts

@@ -0,0 +1,125 @@
+/*
+ * Copyright (c) 2024, NVIDIA CORPORATION.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { OpsBotPlugin } from "../../plugin";
+import { PayloadRepository } from "../../types";
+import { isVersionedBranch, getVersionFromBranch } from "../../shared";
+import { basename } from "path";
+import { Context } from "probot";
+
+export class ForwardMerger extends OpsBotPlugin {
+  context: Context;
+  currentBranch: string;
+  repo: PayloadRepository;
+
+  constructor(
+    context: Context,
+    private payload: Context<"push">["payload"]
+  ) {
+    super("forward_merger", context);
+    this.context = context;
+    this.currentBranch = basename(this.payload.ref);
+    this.repo = payload.repository;
+  }
+
+  async mergeForward(): Promise<void> {
+    if (await this.pluginIsDisabled()) return;
+
+    if (!isVersionedBranch(this.currentBranch)) {
+      this.logger.info("Will not merge forward on non-versioned branch");
+      return;
+    }
+
+    const branches = await this.getBranches();
+    const sortedBranches = this.sortBranches(branches);
+    const nextBranch = this.getNextBranch(sortedBranches);
+
+    if (!nextBranch) return;
+
+    const { data: pr } = await this.context.octokit.pulls.create({
+      owner: this.repo.owner.login,
+      repo: this.repo.name,
+      title: "Forward-merge " + this.currentBranch + " into " + nextBranch,
+      head: this.currentBranch,
+      base: nextBranch,
+      maintainer_can_modify: false,
+      body: `Forward-merge triggered by push to ${this.currentBranch} that creates a PR to keep ${nextBranch} up-to-date. If this PR is unable to be immediately merged due to conflicts, it will remain open for the team to manually merge. See [forward-merger docs](https://docs.rapids.ai/maintainers/forward-merger/) for more info.`,
+    });
+
+    try {
+      this.logger.info("Merging PR");
+      await this.context.octokit.pulls.merge({
+        owner: this.repo.owner.login,
+        repo: this.repo.name,
+        pull_number: pr.number,
+        sha: pr.head.sha,
+      });
+    } catch (error) {
+      await this.issueComment(
+        pr.number,
+        "**FAILURE** - Unable to forward-merge due to an error, **manual** merge is necessary. Do not use the `Resolve conflicts` option in this PR, follow these instructions https://docs.rapids.ai/maintainers/forward-merger/ \n **IMPORTANT**: When merging this PR, do not use the [auto-merger](https://docs.rapids.ai/resources/auto-merger/) (i.e. the `/merge` comment). Instead, an admin must manually merge by changing the merging strategy to `Create a Merge Commit`. Otherwise, history will be lost and the branches become incompatible."
+      );
+      return;
+    }
+
+    await this.issueComment(
+      pr.number,
+      "**SUCCESS** - forward-merge complete."
+    );
+  }
+
+  async getBranches(): Promise<string[]> {
+    const branches = await this.context.octokit.paginate(
+      this.context.octokit.repos.listBranches,
+      {
+        owner: this.repo.owner.login,
+        repo: this.repo.name,
+      }
+    );
+    return branches
+      .filter((branch) => isVersionedBranch(branch.name))
+      .map((branch) => branch.name);
+  }
+
+  sortBranches(branches: string[]): string[] {
+    return branches.sort((a, b) => {
+      const [yearA, monthA] = getVersionFromBranch(a).split(".").map(Number);
+      const [yearB, monthB] = getVersionFromBranch(b).split(".").map(Number);
+      if (yearA !== yearB) {
+        return yearA - yearB;
+      } else {
+        return monthA - monthB;
+      }
+    });
+  }
+
+  getNextBranch(sortedBranches: string[]): string | undefined {
+    const currentBranchIndex = sortedBranches.findIndex(
+      (branch) => branch === this.currentBranch
+    );
+    const nextBranch = sortedBranches[currentBranchIndex + 1];
+    return nextBranch;
+  }
+
+  async issueComment(id, comment): Promise<void> {
+    await this.context.octokit.issues.createComment({
+      owner: this.repo.owner.login,
+      repo: this.repo.name,
+      issue_number: id,
+      body: comment,
+    });
+  }
+}

src/plugins/ForwardMerger/index.ts

@@ -0,0 +1,24 @@
+/*
+* Copyright (c) 2024, NVIDIA CORPORATION.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*     http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+import { Probot } from "probot";
+import { ForwardMerger } from "./forward_merger";
+
+export const initForwardMerger = (app: Probot) => {
+  app.on(["push"], async (context) => {
+    await new ForwardMerger(context, context.payload).mergeForward();
+  });
+};

test/fixtures/contexts/base.ts

@@ -35,6 +35,8 @@ import {
   mockPaginate,
   mockPullsGet,
   mockUpdateRelease,
+  mockCreatePR,
+  mockListBranches,
 } from "../../mocks";
 import type { EmitterWebhookEventName } from "@octokit/webhooks/dist-types/types";
 
@@ -57,6 +59,7 @@ export const makeContext = (payload, name: EmitterWebhookEventName) => {
         list: mockListPulls,
         listReviews: mockListReviews,
         merge: mockMerge,
+        create: mockCreatePR,
       },
       repos: {
         createCommitStatus: mockCreateCommitStatus,
@@ -66,6 +69,7 @@ export const makeContext = (payload, name: EmitterWebhookEventName) => {
         getReleaseByTag: mockGetReleaseByTag,
         updateRelease: mockUpdateRelease,
         compareCommitsWithBasehead: mockCompareCommitsWithBasehead,
+        listBranches: mockListBranches,
       },
       users: {
         getByUsername: mockGetByUsername,