Use commit author when pull request user is "ghost".

GitHub does allow the removal of a user without
removing its own pending commits in pull requests.
Example: https://github.com/jenkinsci/appaloosa-plugin/pull/3

When importing those commits into Gerrit, the only
valid clue on who was the owner of the pull request is
actually the associated Git commits author.

Change-Id: I7543a5c3f116db5fce0479209be63ccc80e331de

github-plugin/src/main/java/com/google/gerrit/server/account/AccountImpoter.java

diff --git a/github-plugin/src/main/java/com/google/gerrit/server/account/AccountImpoter.java b/github-plugin/src/main/java/com/google/gerrit/server/account/AccountImpoter.java
index 7d96b56..6f643b9 100644
--- a/github-plugin/src/main/java/com/google/gerrit/server/account/AccountImpoter.java
+++ b/github-plugin/src/main/java/com/google/gerrit/server/account/AccountImpoter.java
@@ -36,21 +36,21 @@
     this.createAccountFactory = createAccountFactory;
   }
 
-  public Account.Id importAccount(GHUser user) throws IOException,
+  public Account.Id importAccount(String login, String name, String email) throws IOException,
       BadRequestException, ResourceConflictException,
       UnprocessableEntityException, OrmException {
-    CreateAccount createAccount = createAccountFactory.create(user.getLogin());
+    CreateAccount createAccount = createAccountFactory.create(login);
     CreateAccount.Input accountInput = new CreateAccount.Input();
-    accountInput.email = user.getEmail();
-    accountInput.name = user.getName();
-    accountInput.username = user.getLogin();
+    accountInput.email = email;
+    accountInput.name = name;
+    accountInput.username = login;
     Response<AccountInfo> accountResponse =
         (Response<AccountInfo>) createAccount.apply(TopLevelResource.INSTANCE,
             accountInput);
     if (accountResponse.statusCode() == HttpStatus.SC_CREATED) {
       return accountResponse.value()._id;
     } else {
-      throw new IOException("Cannot import GitHub account " + user.getLogin()
+      throw new IOException("Cannot import GitHub account " + login
           + ": HTTP Status " + accountResponse.statusCode());
     }
   }

github-plugin/src/main/java/com/googlesrouce/gerrit/plugins/github/git/PullRequestImportJob.java

diff --git a/github-plugin/src/main/java/com/googlesrouce/gerrit/plugins/github/git/PullRequestImportJob.java b/github-plugin/src/main/java/com/googlesrouce/gerrit/plugins/github/git/PullRequestImportJob.java
index 05bb0ba..c4a7673 100644
--- a/github-plugin/src/main/java/com/googlesrouce/gerrit/plugins/github/git/PullRequestImportJob.java
+++ b/github-plugin/src/main/java/com/googlesrouce/gerrit/plugins/github/git/PullRequestImportJob.java
@@ -34,6 +34,7 @@
 import org.eclipse.jgit.transport.RefSpec;
 import org.kohsuke.github.GHPullRequest;
 import org.kohsuke.github.GHPullRequestCommitDetail;
+import org.kohsuke.github.GHPullRequestCommitDetail.Authorship;
 import org.kohsuke.github.GHRepository;
 import org.kohsuke.github.GHUser;
 import org.slf4j.Logger;
@@ -185,8 +186,8 @@
     return e.getLocalizedMessage();
   }
 
-  private List<Id> addPullRequestToChange(ReviewDb db, GHPullRequest pr, Repository gitRepo)
-      throws Exception {
+  private List<Id> addPullRequestToChange(ReviewDb db, GHPullRequest pr,
+      Repository gitRepo) throws Exception {
     String destinationBranch = pr.getBase().getRef();
     List<Id> prChanges = Lists.newArrayList();
     ObjectId baseObjectId = ObjectId.fromString(pr.getBase().getSha());
@@ -203,10 +204,21 @@
           + ": Inserting PullRequest into Gerrit");
       RevCommit revCommit =
           walk.parseCommit(ObjectId.fromString(ghCommitDetail.getSha()));
-      Account.Id pullRequestOwner = getOrRegisterAccount(db, pr.getUser());
+
+      Account.Id pullRequestOwner;
+      // It may happen that the user that created the Pull Request has been
+      // removed from GitHub: we assume that the commit author was that user
+      // as there are no other choices.
+      if (pr.getUser() == null) {
+        pullRequestOwner = getOrRegisterAccount(db, ghCommitDetail.getCommit().getAuthor());
+      } else {
+        pullRequestOwner = getOrRegisterAccount(db, pr.getUser());
+      }
+
       Id changeId =
-          createChange.addCommitToChange(db, project, gitRepo, destinationBranch,
-              pullRequestOwner, revCommit, getChangeMessage(pr),
+          createChange.addCommitToChange(db, project, gitRepo,
+              destinationBranch, pullRequestOwner, revCommit,
+              getChangeMessage(pr),
               String.format(TOPIC_FORMAT, pr.getNumber()), false);
       if (changeId != null) {
         prChanges.add(changeId);
@@ -216,19 +228,34 @@
     return prChanges;
   }
 
-  private com.google.gerrit.reviewdb.client.Account.Id getOrRegisterAccount(ReviewDb db,
-      GHUser user) throws OrmException, BadRequestException,
+  private com.google.gerrit.reviewdb.client.Account.Id getOrRegisterAccount(
+      ReviewDb db, Authorship author) throws BadRequestException,
+      ResourceConflictException, UnprocessableEntityException, OrmException,
+      IOException {
+    return getOrRegisterAccount(db, author.getName(), author.getName(),
+        author.getEmail());
+  }
+
+  private com.google.gerrit.reviewdb.client.Account.Id getOrRegisterAccount(
+      ReviewDb db, GHUser user) throws OrmException, BadRequestException,
       ResourceConflictException, UnprocessableEntityException, IOException {
-      AccountExternalId.Key userExtKey =
-          new AccountExternalId.Key(AccountExternalId.SCHEME_USERNAME,
-              user.getLogin());
-      AccountExternalIdAccess gerritExtIds = db.accountExternalIds();
-      AccountExternalId userExtId = gerritExtIds.get(userExtKey);
-      if (userExtId == null) {
-        return accountImporter.importAccount(user);
-      } else {
-        return userExtId.getAccountId();
-      }
+    return getOrRegisterAccount(db, user.getLogin(), user.getName(),
+        user.getEmail());
+  }
+
+  private com.google.gerrit.reviewdb.client.Account.Id getOrRegisterAccount(
+      ReviewDb db, String login, String name, String email)
+      throws OrmException, BadRequestException, ResourceConflictException,
+      UnprocessableEntityException, IOException {
+    AccountExternalId.Key userExtKey =
+        new AccountExternalId.Key(AccountExternalId.SCHEME_USERNAME, login);
+    AccountExternalIdAccess gerritExtIds = db.accountExternalIds();
+    AccountExternalId userExtId = gerritExtIds.get(userExtKey);
+    if (userExtId == null) {
+      return accountImporter.importAccount(login, name, email);
+    } else {
+      return userExtId.getAccountId();
+    }
   }
 
   private String getChangeMessage(GHPullRequest pr) {