feat(import): Add --preserve-commit

commands/import/README.md

@@ -52,3 +52,13 @@ When importing repositories, you can specify the destination directory by the di
 ```
 $ lerna import ~/Product --dest=utilities
 ```
+
+### `--preserve-commit`
+
+Each git commit has an **author** and a **committer** (with a separate date for each). Usually they're the same person (and date), but since `lerna import` re-creates each commit from the external repository, the **committer** becomes the current git user (and date). This is *technically* correct, but may be undesireable, for example, on Github, which displays both the **author** and **committer** if they're different people, leading to potentially confusing history/blames on imported commits.
+
+Enabling this option preserves the original **committer** (and commit date) to avoid such issues.
+
+```
+$ lerna import ~/Product --preserve-commit
+```

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

@@ -154,6 +154,39 @@ describe("ImportCommand", () => {
       expect(await lastCommitInDir(testDir)).toBe("Init commit");
     });
 
+    it("preserves original committer and date with --preserve-commit", async () =>
+      Promise.all(
+        // running the same test with and without --preserve-commit
+        [true, false].map(async shouldPreserve => {
+          const [testDir, externalDir] = await initBasicFixtures();
+          const filePath = path.join(externalDir, "old-file");
+          let expectedEmail;
+          let expectedName;
+
+          await execa("git", ["config", "user.name", "'test-name'"], { cwd: externalDir });
+          await execa("git", ["config", "user.email", "'test-email@foo.bar'"], { cwd: externalDir });
+          await fs.writeFile(filePath, "non-empty content");
+          await gitAdd(externalDir, filePath);
+          await gitCommit(externalDir, "Non-empty commit");
+
+          if (shouldPreserve) {
+            await lernaImport(testDir)(externalDir, "--preserve-commit");
+            // original committer
+            expectedEmail = "test-email@foo.bar";
+            expectedName = "test-name";
+          } else {
+            await lernaImport(testDir)(externalDir);
+            // whatever the current git user is
+            expectedEmail = execa.sync("git", ["config", "user.email"], { cwd: testDir }).stdout;
+            expectedName = execa.sync("git", ["config", "user.name"], { cwd: testDir }).stdout;
+          }
+
+          expect(execa.sync("git", ["log", "-1", "--format=%cn <%ce>"], { cwd: testDir }).stdout).toBe(
+            `${expectedName} <${expectedEmail}>`
+          );
+        })
+      ));
+
     it("allows skipping confirmation prompt", async () => {
       const [testDir, externalDir] = await initBasicFixtures();
       await lernaImport(testDir)(externalDir, "--yes");

commands/import/command.js

@@ -21,6 +21,11 @@ exports.builder = yargs =>
         describe: "Import destination directory for the external git repository",
         type: "string",
       },
+      "preserve-commit": {
+        group: "Command Options:",
+        describe: "Preserve original committer in addition to original author",
+        type: "boolean",
+      },
       y: {
         group: "Command Options:",
         describe: "Skip all confirmation prompts",

commands/import/index.js

@@ -94,10 +94,16 @@ class ImportCommand extends Command {
       throw new ValidationError("NOCOMMITS", `No git commits to import at "${inputPath}"`);
     }
 
+    if (this.options.preserveCommit) {
+      // Back these up since they'll change for each commit
+      this.origGitEmail = this.execSync("git", ["config", "user.email"]);
+      this.origGitName = this.execSync("git", ["config", "user.name"]);
+    }
+
     // Stash the repo's pre-import head away in case something goes wrong.
     this.preImportHead = this.getCurrentSHA();
 
-    if (ChildProcessUtilities.execSync("git", ["diff-index", "HEAD"], this.execOpts)) {
+    if (this.execSync("git", ["diff-index", "HEAD"])) {
       throw new ValidationError("ECHANGES", "Local repository has un-committed changes");
     }
 
@@ -126,11 +132,15 @@ class ImportCommand extends Command {
   }
 
   getCurrentSHA() {
-    return ChildProcessUtilities.execSync("git", ["rev-parse", "HEAD"], this.execOpts);
+    return this.execSync("git", ["rev-parse", "HEAD"]);
   }
 
   getWorkspaceRoot() {
-    return ChildProcessUtilities.execSync("git", ["rev-parse", "--show-toplevel"], this.execOpts);
+    return this.execSync("git", ["rev-parse", "--show-toplevel"]);
+  }
+
+  execSync(cmd, args) {
+    return ChildProcessUtilities.execSync(cmd, args, this.execOpts);
   }
 
   externalExecSync(cmd, args) {
@@ -186,6 +196,18 @@ class ImportCommand extends Command {
       .replace(/^(rename (from|to)) /gm, `$1 ${formattedTarget}/`);
   }
 
+  getGitUserFromSha(sha) {
+    return {
+      email: this.externalExecSync("git", ["show", "-s", "--format='%ae'", sha]),
+      name: this.externalExecSync("git", ["show", "-s", "--format='%an'", sha]),
+    };
+  }
+
+  configureGitUser({ email, name }) {
+    this.execSync("git", ["config", "user.email", `"${email}"`]);
+    this.execSync("git", ["config", "user.name", `"${name}"`]);
+  }
+
   execute() {
     this.enableProgressBar();
 
@@ -194,13 +216,19 @@ class ImportCommand extends Command {
       tracker.info(sha);
 
       const patch = this.createPatchForCommit(sha);
+      const procArgs = ["am", "-3", "--keep-non-patch"];
+
+      if (this.options.preserveCommit) {
+        this.configureGitUser(this.getGitUserFromSha(sha));
+        procArgs.push("--committer-date-is-author-date");
+      }
 
       // Apply the modified patch to the current lerna repository, preserving
       // original commit date, author and message.
       //
       // Fall back to three-way merge, which can help with duplicate commits
       // due to merge history.
-      const proc = ChildProcessUtilities.exec("git", ["am", "-3", "--keep-non-patch"], this.execOpts);
+      const proc = ChildProcessUtilities.exec("git", procArgs, this.execOpts);
 
       proc.stdin.end(patch);
 
@@ -227,16 +255,30 @@ class ImportCommand extends Command {
       .then(() => {
         tracker.finish();
 
+        if (this.options.preserveCommit) {
+          this.configureGitUser({
+            email: this.origGitEmail,
+            name: this.origGitName,
+          });
+        }
+
         this.logger.success("import", "finished");
       })
       .catch(err => {
         tracker.finish();
 
+        if (this.options.preserveCommit) {
+          this.configureGitUser({
+            email: this.origGitEmail,
+            name: this.origGitName,
+          });
+        }
+
         this.logger.error("import", `Rolling back to previous HEAD (commit ${this.preImportHead})`);
 
         // Abort the failed `git am` and roll back to previous HEAD.
-        ChildProcessUtilities.execSync("git", ["am", "--abort"], this.execOpts);
-        ChildProcessUtilities.execSync("git", ["reset", "--hard", this.preImportHead], this.execOpts);
+        this.execSync("git", ["am", "--abort"]);
+        this.execSync("git", ["reset", "--hard", this.preImportHead]);
 
         throw new ValidationError(
           "EIMPORT",