feat(publish): Add --amend flag (#1422)

For the CI/CD use case of releasing-per-commit, adding a commit to update
the version number and/or the CHANGELOG, for every merged patch, creates
unnecessary noise. This patch allows us to amend the existing commit with any
new changes, without replacing the message or generating a new commit.

- Added the `--amend` commandline flag to the publish command
- Add an 'amend' flag to the git-commit helper, which translates into
  `--amend --no-edit`.
- Added tests for all the above.
- Updated the README.md flag with the new option.

.travis.yml

@@ -13,6 +13,7 @@ node_js:
 env:
   global:
     - NO_UPDATE_NOTIFIER=1
+    - NODE_NO_WARNINGS=1
 
 matrix:
   fast_finish: true

README.md

@@ -494,6 +494,19 @@ This can be configured in lerna.json, as well:
 }
 ```
 
+#### --amend
+
+```sh
+$ lerna publish --amend
+# commit message is retained, and `git push` is skipped.
+```
+
+When run with this flag, `publish` will perform all changes on the current commit, instead of adding a new one. This is
+useful during [Continuous integration (CI)](https://en.wikipedia.org/wiki/Continuous_integration), to reduce the number
+of commits in the projects' history.
+
+In order to prevent unintended overwrites, this command will skip `git push`.
+
 #### --allow-branch [glob]
 
 Lerna allows you to specify a glob or an array of globs in your `lerna.json` that your current branch needs to match to be publishable.

appveyor.yml

@@ -5,6 +5,7 @@ shallow_clone: true
 
 environment:
   NO_UPDATE_NOTIFIER: "1"
+  NODE_NO_WARNINGS: "1"
   matrix:
     - nodejs_version: "10"
     - nodejs_version: "8"

commands/publish/__tests__/git-commit.test.js

@@ -31,3 +31,18 @@ test("multiline message", async () => {
   expect(subject).toBe("foo");
   expect(body).toBe("bar");
 });
+
+test("amend", async () => {
+  const cwd = await initFixture("root-manifest-only");
+
+  await fs.outputFile(path.join(cwd, "packages", "pkg-4", "index.js"), "hello");
+  await execa("git", ["add", "."], { cwd });
+  await gitCommit(`foo${EOL}${EOL}bar`, { cwd, amend: true });
+
+  const subject = await execa.stdout("git", ["log", "-1", "--pretty=format:%s"], { cwd });
+  const body = await execa.stdout("git", ["log", "-1", "--pretty=format:%b"], { cwd });
+
+  // It should ignore any message.
+  expect(subject).toBe("Init commit");
+  expect(body).toBe("");
+});

commands/publish/__tests__/publish-command.test.js

@@ -25,6 +25,7 @@ const gitTag = require("@lerna-test/git-tag");
 const gitCommit = require("@lerna-test/git-commit");
 const initFixture = require("@lerna-test/init-fixture")(__dirname);
 const showCommit = require("@lerna-test/show-commit");
+const getCommitMessage = require("@lerna-test/get-commit-message");
 
 // file under test
 const lernaPublish = require("@lerna-test/command-runner")(require("../command"));
@@ -169,6 +170,34 @@ describe("PublishCommand", () => {
     });
   });
 
+  describe("--amend", () => {
+    it("commits changes on the previous commit", async () => {
+      const testDir = await initFixture("normal");
+      await lernaPublish(testDir)("--amend");
+
+      const message = await getCommitMessage(testDir);
+      expect(message).toMatch("Init commit");
+    });
+
+    it("ignores custom messages", async () => {
+      const testDir = await initFixture("normal");
+      await lernaPublish(testDir)("--message", "chore: Release %v :rocket:", "--amend");
+
+      const message = await getCommitMessage(testDir);
+      expect(message).toMatch("Init commit");
+    });
+  });
+
+  describe("--amend --independent", () => {
+    it("commits changes with a custom message", async () => {
+      const testDir = await initFixture("independent");
+      await lernaPublish(testDir)("--amend");
+
+      const message = await getCommitMessage(testDir);
+      expect(message).toMatch("Init commit");
+    });
+  });
+
   describe("when local clone is behind upstream", () => {
     it("throws an error during interactive publish", async () => {
       const testDir = await initFixture("normal");

commands/publish/command.js

@@ -68,6 +68,11 @@ exports.builder = yargs => {
       type: "string",
       requiresArg: true,
     },
+    amend: {
+      describe: "Amend the existing commit, instead of generating a new one.",
+      type: "boolean",
+      default: false,
+    },
     "npm-tag": {
       describe: "Publish packages with the specified npm dist-tag",
       type: "string",

commands/publish/index.js

@@ -52,13 +52,17 @@ class PublishCommand extends Command {
       tempTag: false,
       yes: false,
       allowBranch: false,
+      amend: false,
     });
   }
 
   initialize() {
     this.gitRemote = this.options.gitRemote || "origin";
     this.gitEnabled = !(this.options.canary || this.options.skipGit);
 
+    // Set the 'amend' flag so it can be passed to child commands.
+    this.execOpts.amend = this.options.amend === true;
+
     // https://docs.npmjs.com/misc/config#save-prefix
     this.savePrefix = this.options.exact ? "" : "^";
 
@@ -205,7 +209,7 @@ class PublishCommand extends Command {
       tasks.push(() => this.publishPackagesToNpm());
     }
 
-    if (this.gitEnabled) {
+    if (this.gitEnabled && !this.options.amend) {
       tasks.push(() => this.pushToRemote());
     }
 

commands/publish/lib/git-commit.js

@@ -11,7 +11,9 @@ function gitCommit(message, opts) {
   log.silly("gitCommit", message);
   const args = ["commit", "--no-verify"];
 
-  if (message.indexOf(EOL) > -1) {
+  if (opts && opts.amend === true) {
+    args.push("--amend", "--no-edit");
+  } else if (message.indexOf(EOL) > -1) {
     // Use tempfile to allow multi\nline strings.
     args.push("-F", tempWrite.sync(message, "lerna-commit.txt"));
   } else {