Add backport action (#17212)

tools/actions/backport/action.yml

@@ -0,0 +1,20 @@
+name: 'PR Backporter'
+description: 'Backports a pull request to a branch using the "/backport to <branch>" comment'
+inputs:
+  target_branch:
+    description: 'Backport target branch.'
+  auth_token:
+    description: 'The token used to authenticate to GitHub.'
+  pr_title_template:
+      description: 'The template used for the PR title. Special placeholder tokens that will be replaced with a value: %target_branch%, %source_pr_title%, %source_pr_number%, %cc_users%.'
+      default: '[%target_branch%] %source_pr_title%'
+  pr_description_template:
+    description: 'The template used for the PR description. Special placeholder tokens that will be replaced with a value: %target_branch%, %source_pr_title%, %source_pr_number%, %cc_users%.'
+    default: |
+      Backport of #%source_pr_number% to %target_branch%
+
+      /cc %cc_users%
+
+runs:
+  using: 'node12'
+  main: 'index.js'

tools/actions/backport/index.js

@@ -0,0 +1,157 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// from https://github.com/dotnet/runtime/blob/main/eng/actions/backport/index.js
+
+function BackportException(message, postToGitHub = true) {
+    this.message = message;
+    this.postToGitHub = postToGitHub;
+  }
+
+  async function run() {
+    const util = require("util");
+    const jsExec = util.promisify(require("child_process").exec);
+
+    console.log("Installing npm dependencies");
+    const { stdout, stderr } = await jsExec("npm install @actions/core @actions/github @actions/exec");
+    console.log("npm-install stderr:\n\n" + stderr);
+    console.log("npm-install stdout:\n\n" + stdout);
+    console.log("Finished installing npm dependencies");
+
+    const core = require("@actions/core");
+    const github = require("@actions/github");
+    const exec = require("@actions/exec");
+
+    const repo_owner = github.context.payload.repository.owner.login;
+    const repo_name = github.context.payload.repository.name;
+    const pr_number = github.context.payload.issue.number;
+    const comment_user = github.context.payload.comment.user.login;
+
+    let octokit = github.getOctokit(core.getInput("auth_token", { required: true }));
+    let target_branch = core.getInput("target_branch", { required: true });
+
+    try {
+      // verify the comment user is a repo collaborator
+      try {
+        await octokit.rest.repos.checkCollaborator({
+          owner: repo_owner,
+          repo: repo_name,
+          username: comment_user
+        });
+        console.log(`Verified ${comment_user} is a repo collaborator.`);
+      } catch (error) {
+        console.log(error);
+        throw new BackportException(`Error: @${comment_user} is not a repo collaborator, backporting is not allowed. If you're a collaborator please make sure your Microsoft team membership visibility is set to Public on https://github.com/orgs/microsoft/people?query=${comment_user}`);
+      }
+
+      try { await exec.exec(`git ls-remote --exit-code --heads origin ${target_branch}`) } catch { throw new BackportException(`Error: The specified backport target branch ${target_branch} wasn't found in the repo.`); }
+      console.log(`Backport target branch: ${target_branch}`);
+
+      console.log("Applying backport patch");
+
+      await exec.exec(`git checkout ${target_branch}`);
+      await exec.exec(`git clean -xdff`);
+
+      // configure git
+      await exec.exec(`git config user.name "github-actions"`);
+      await exec.exec(`git config user.email "github-actions@github.com"`);
+
+      // create temporary backport branch
+      const temp_branch = `backport/pr-${pr_number}-to-${target_branch}`;
+      await exec.exec(`git checkout -b ${temp_branch}`);
+
+      // skip opening PR if the branch already exists on the origin remote since that means it was opened
+      // by an earlier backport and force pushing to the branch updates the existing PR
+      let should_open_pull_request = true;
+      try {
+        await exec.exec(`git ls-remote --exit-code --heads origin ${temp_branch}`);
+        should_open_pull_request = false;
+      } catch { }
+
+      // download and apply patch
+      await exec.exec(`curl -sSL "${github.context.payload.issue.pull_request.patch_url}" --output changes.patch`);
+
+      const git_am_command = "git am --3way --ignore-whitespace --keep-non-patch changes.patch";
+      let git_am_output = `$ ${git_am_command}\n\n`;
+      let git_am_failed = false;
+      try {
+        await exec.exec(git_am_command, [], {
+          listeners: {
+            stdout: function stdout(data) { git_am_output += data; },
+            stderr: function stderr(data) { git_am_output += data; }
+          }
+        });
+      } catch (error) {
+        git_am_output += error;
+        git_am_failed = true;
+      }
+
+      if (git_am_failed) {
+        const git_am_failed_body = `@${github.context.payload.comment.user.login} backporting to ${target_branch} failed, the patch most likely resulted in conflicts:\n\n\`\`\`shell\n${git_am_output}\n\`\`\`\n\nPlease backport manually!`;
+        await octokit.rest.issues.createComment({
+          owner: repo_owner,
+          repo: repo_name,
+          issue_number: pr_number,
+          body: git_am_failed_body
+        });
+        throw new BackportException("Error: git am failed, most likely due to a merge conflict.", false);
+      }
+      else {
+        // push the temp branch to the repository
+        await exec.exec(`git push --force --set-upstream origin HEAD:${temp_branch}`);
+      }
+
+      if (!should_open_pull_request) {
+        console.log("Backport temp branch already exists, skipping opening a PR.");
+        return;
+      }
+
+      // prepate the GitHub PR details
+      let backport_pr_title = core.getInput("pr_title_template");
+      let backport_pr_description = core.getInput("pr_description_template");
+
+      // get users to cc (append PR author if different from user who issued the backport command)
+      let cc_users = `@${comment_user}`;
+      if (comment_user != github.context.payload.issue.user.login) cc_users += ` @${github.context.payload.issue.user.login}`;
+
+      // replace the special placeholder tokens with values
+      backport_pr_title = backport_pr_title
+        .replace(/%target_branch%/g, target_branch)
+        .replace(/%source_pr_title%/g, github.context.payload.issue.title)
+        .replace(/%source_pr_number%/g, github.context.payload.issue.number)
+        .replace(/%cc_users%/g, cc_users);
+
+      backport_pr_description = backport_pr_description
+        .replace(/%target_branch%/g, target_branch)
+        .replace(/%source_pr_title%/g, github.context.payload.issue.title)
+        .replace(/%source_pr_number%/g, github.context.payload.issue.number)
+        .replace(/%cc_users%/g, cc_users);
+
+      // open the GitHub PR
+      await octokit.rest.pulls.create({
+        owner: repo_owner,
+        repo: repo_name,
+        title: backport_pr_title,
+        body: backport_pr_description,
+        head: temp_branch,
+        base: target_branch
+      });
+
+      console.log("Successfully opened the GitHub PR.");
+    } catch (error) {
+
+      core.setFailed(error);
+
+      if (error.postToGitHub === undefined || error.postToGitHub == true) {
+        // post failure to GitHub comment
+        const unknown_error_body = `@${comment_user} an error occurred while backporting to ${target_branch}, please check the run log for details!\n\n${error.message}`;
+        await octokit.rest.issues.createComment({
+          owner: repo_owner,
+          repo: repo_name,
+          issue_number: pr_number,
+          body: unknown_error_body
+        });
+      }
+    }
+  }
+
+  run();