Don't amend commits with different author

Summary: Also delete extra newlines.

Test Plan:
  $ arc diff # on top of my commit

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2025

Differential Revision: https://secure.phabricator.com/D3996

src/repository/api/ArcanistGitAPI.php

@@ -472,6 +472,18 @@ final class ArcanistGitAPI extends ArcanistRepositoryAPI {
     return $this->status;
   }
 
+  public function getGitConfig($key, $default = null) {
+    list($stdout) = $this->execxLocal('config %s', $key);
+    if ($stdout == '') {
+      return $default;
+    }
+    return rtrim($stdout);
+  }
+
+  public function getAuthor() {
+    return $this->getGitConfig('user.name');
+  }
+
   public function addToCommit(array $paths) {
     $this->execxLocal(
       'add -- %Ls',

src/repository/api/ArcanistMercurialAPI.php

@@ -594,6 +594,18 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
     $this->execxLocal('up');
   }
 
+  private function getMercurialConfig($key, $default = null) {
+    list($stdout) = $this->execxLocal('showconfig %s', $key);
+    if ($stdout == '') {
+      return $default;
+    }
+    return rtrim($stdout);
+  }
+
+  public function getAuthor() {
+    return $this->getMercurialConfig('ui.username');
+  }
+
   public function addToCommit(array $paths) {
     $this->execxLocal(
       'add -- %Ls',

src/repository/api/ArcanistRepositoryAPI.php

@@ -192,6 +192,10 @@ abstract class ArcanistRepositoryAPI {
     throw new ArcanistCapabilityNotSupportedException($this);
   }
 
+  public function getAuthor() {
+    throw new ArcanistCapabilityNotSupportedException($this);
+  }
+
   public function addToCommit(array $paths) {
     throw new ArcanistCapabilityNotSupportedException($this);
   }

src/workflow/ArcanistBaseWorkflow.php

@@ -795,7 +795,7 @@ abstract class ArcanistBaseWorkflow {
       echo "You have unstaged changes in this working copy.\n\n".
         $working_copy_desc.
         "  Unstaged changes in working copy:\n".
-        "    ".implode("\n    ", $unstaged)."\n\n";
+        "    ".implode("\n    ", $unstaged);
       if ($this->askForAdd()) {
         $api->addToCommit($unstaged);
         $must_commit += array_flip($unstaged);
@@ -815,7 +815,7 @@ abstract class ArcanistBaseWorkflow {
       echo "You have uncommitted changes in this working copy.\n\n".
         $working_copy_desc.
         "  Uncommitted changes in working copy:\n".
-        "    ".implode("\n    ", $uncommitted)."\n\n";
+        "    ".implode("\n    ", $uncommitted);
       if ($this->askForAdd()) {
         $must_commit += array_flip($uncommitted);
       } else {
@@ -853,7 +853,10 @@ abstract class ArcanistBaseWorkflow {
       return false;
     }
 
-    // TODO: Check last commit's author. If not me then return false.
+    if ($api->getAuthor() != $commit['author']) {
+      return false;
+    }
+
     // TODO: Check commits since tracking branch. If empty then return false.
 
     $repository_phid = idx($this->getProjectInfo(), 'repositoryPHID');