NoteDb: Handle leading whitespace in change subjects

JGit's FooterLine parser trims leading spaces (but not all whitespace)
from any values it reads. This means that even though we represent the
leading spaces in subjects faithfully when storing, we can't read it
back out. Handle this minor variation.

Change-Id: I9eb358eecdbf05a0528dfcda9650d714847b0f75

gerrit-server/src/test/java/com/google/gerrit/server/notedb/CommitMessageOutputTest.java

@@ -289,6 +289,43 @@ public class CommitMessageOutputTest extends AbstractChangeNotesTest {
         update.getResult());
   }
 
+  @Test
+  public void leadingWhitespace() throws Exception {
+    Change c = TestChanges.newChange(project, changeOwner.getAccountId());
+    c.setCurrentPatchSet(c.currentPatchSetId(), "  " + c.getSubject(),
+        c.getOriginalSubject());
+    ChangeUpdate update = newUpdate(c, changeOwner);
+    update.setChangeId(c.getKey().get());
+    update.setBranch(c.getDest().get());
+    update.commit();
+
+    assertBodyEquals("Update patch set 1\n"
+        + "\n"
+        + "Patch-set: 1\n"
+        + "Change-id: " + c.getKey().get() + "\n"
+        + "Subject:   Change subject\n"
+        + "Branch: refs/heads/master\n"
+        + "Commit: " + update.getCommit().name() + "\n",
+        update.getResult());
+
+    c = TestChanges.newChange(project, changeOwner.getAccountId());
+    c.setCurrentPatchSet(c.currentPatchSetId(), "\t\t" + c.getSubject(),
+        c.getOriginalSubject());
+    update = newUpdate(c, changeOwner);
+    update.setChangeId(c.getKey().get());
+    update.setBranch(c.getDest().get());
+    update.commit();
+
+    assertBodyEquals("Update patch set 1\n"
+        + "\n"
+        + "Patch-set: 1\n"
+        + "Change-id: " + c.getKey().get() + "\n"
+        + "Subject: \t\tChange subject\n"
+        + "Branch: refs/heads/master\n"
+        + "Commit: " + update.getCommit().name() + "\n",
+        update.getResult());
+  }
+
   private RevCommit parseCommit(ObjectId id) throws Exception {
     if (id instanceof RevCommit) {
       return (RevCommit) id;