feat(git-node): add support for amend! commits (#710)

Commits made using `git commit --fixup=reword:HEAD` are empty commits
that lets the user change the commit message without needing to
force-push the PR branch. With this commit, those are
still ignored when using `--fixupAll` CLI flag.

lib/landing_session.js

@@ -119,10 +119,9 @@ export default class LandingSession extends Session {
     const commitInfo = { base, head, shas: commitShas };
     this.saveCommitInfo(commitInfo);
 
-    const allowEmptyCommits = this.fixupAll ? ['--allow-empty'] : [];
     try {
       await forceRunAsync('git',
-        ['cherry-pick', ...allowEmptyCommits, ...this.gpgSign, `${base}..${head}`],
+        ['cherry-pick', '--allow-empty', ...this.gpgSign, `${base}..${head}`],
         { ignoreFailure: false });
     } catch (ex) {
       cli.error('Failed to apply patches');
@@ -152,11 +151,11 @@ export default class LandingSession extends Session {
 
   getRebaseSuggestion(subjects) {
     const { upstream, branch } = this;
-    let command = `git rebase ${upstream}/${branch} -i`;
+    let command = `git rebase ${upstream}/${branch} --no-keep-empty -i`;
     command += ' -x "git node land --amend"';
 
     const squashes = subjects.filter(
-      line => line.includes('fixup!') || line.includes('squash!'));
+      line => line.includes('fixup!') || line.includes('squash!') || line.includes('amend!'));
 
     if (squashes.length !== 0) {
       command += ' --autosquash';
@@ -233,7 +232,8 @@ export default class LandingSession extends Session {
       const msgAmend = `-x "git node land --amend ${assumeYes}"`;
       try {
         await forceRunAsync('git',
-          ['rebase', ...this.gpgSign, `${upstream}/${branch}`, '-i', '--autosquash', msgAmend],
+          ['rebase', ...this.gpgSign, `${upstream}/${branch}`,
+            '--no-keep-empty', '-i', '--autosquash', msgAmend],
           {
             ignoreFailure: false,
             spawnArgs: {