Merge pull request #1635 from atom/aw/undo-first-commit

Undo an initial commit

lib/git-shell-out-strategy.js

@@ -812,6 +812,10 @@ export default class GitShellOutStrategy {
     return this.exec(['reset', `--${type}`, revision]);
   }
 
+  deleteRef(ref) {
+    return this.exec(['update-ref', '-d', ref]);
+  }
+
   /**
    * Branches
    */

lib/models/repository-states/present.js

@@ -341,7 +341,18 @@ export default class Present extends State {
         ...Keys.filePatch.eachWithOpts({staged: true}),
         Keys.headDescription,
       ],
-      () => this.git().reset('soft', 'HEAD~'),
+      async () => {
+        try {
+          await this.git().reset('soft', 'HEAD~');
+        } catch (e) {
+          if (/unknown revision/.test(e.stdErr)) {
+            // Initial commit
+            await this.git().deleteRef('HEAD');
+          } else {
+            throw e;
+          }
+        }
+      },
     );
   }
 

test/git-strategies.test.js

@@ -714,6 +714,31 @@ import * as reporterProxy from '../lib/reporter-proxy';
       });
     });
 
+    describe('deleteRef()', function() {
+      it('soft-resets an initial commit', async function() {
+        const workingDirPath = await cloneRepository('three-files');
+        const git = createTestStrategy(workingDirPath);
+
+        // Ensure that three-files still has only a single commit
+        assert.lengthOf(await git.getCommits({max: 10}), 1);
+
+        // Put something into the index to ensure it doesn't get lost
+        fs.appendFileSync(path.join(workingDirPath, 'a.txt'), 'zzz\n', 'utf8');
+        await git.exec(['add', '.']);
+
+        await git.deleteRef('HEAD');
+
+        const after = await git.getCommit('HEAD');
+        assert.isTrue(after.unbornRef);
+
+        const stagedChanges = await git.getDiffsForFilePath('a.txt', {staged: true});
+        assert.lengthOf(stagedChanges, 1);
+        const stagedChange = stagedChanges[0];
+        assert.strictEqual(stagedChange.newPath, 'a.txt');
+        assert.deepEqual(stagedChange.hunks[0].lines, ['+foo', '+zzz']);
+      });
+    });
+
     describe('getBranches()', function() {
       const sha = '66d11860af6d28eb38349ef83de475597cb0e8b4';
 

test/models/repository.test.js

@@ -575,6 +575,63 @@ describe('Repository', function() {
     });
   });
 
+  describe('undoLastCommit()', function() {
+    it('performs a soft reset', async function() {
+      const workingDirPath = await cloneRepository('multiple-commits');
+      const repo = new Repository(workingDirPath);
+      await repo.getLoadPromise();
+
+      fs.appendFileSync(path.join(workingDirPath, 'file.txt'), 'qqq\n', 'utf8');
+      await repo.git.exec(['add', '.']);
+      await repo.git.commit('add stuff');
+
+      const parentCommit = await repo.git.getCommit('HEAD~');
+
+      await repo.undoLastCommit();
+
+      const commitAfterReset = await repo.git.getCommit('HEAD');
+      assert.strictEqual(commitAfterReset.sha, parentCommit.sha);
+
+      const fp = await repo.getFilePatchForPath('file.txt', {staged: true});
+      assert.strictEqual(
+        fp.toString(),
+        dedent`
+          diff --git a/file.txt b/file.txt
+          --- a/file.txt
+          +++ b/file.txt
+          @@ -1,1 +1,2 @@
+           three
+          +qqq\n
+        `,
+      );
+    });
+
+    it('deletes the HEAD ref when only a single commit is present', async function() {
+      const workingDirPath = await cloneRepository('three-files');
+      const repo = new Repository(workingDirPath);
+      await repo.getLoadPromise();
+
+      fs.appendFileSync(path.join(workingDirPath, 'b.txt'), 'qqq\n', 'utf8');
+      await repo.git.exec(['add', '.']);
+
+      await repo.undoLastCommit();
+
+      const fp = await repo.getFilePatchForPath('b.txt', {staged: true});
+      assert.strictEqual(
+        fp.toString(),
+        dedent`
+          diff --git a/b.txt b/b.txt
+          new file mode 100644
+          --- /dev/null
+          +++ b/b.txt
+          @@ -0,0 +1,2 @@
+          +bar
+          +qqq\n
+        `,
+      );
+    });
+  });
+
   describe('fetch(branchName, {remoteName})', function() {
     it('brings commits from the remote and updates remote branch, and does not update branch', async function() {
       const {localRepoPath} = await setUpLocalAndRemoteRepositories({remoteAhead: true});