Add user preference for auto-selecting a base for merges

For reviewing merge commits most users expect to the see the full diff
that is integrated by accepting the merge commit. This diff is
available if the user selects 'Parent 1' from the 'Diff against'
drop-down list, however this is a new feature and most users don't
know about. Also it is inconvenient to manually select the first
parent for every merge. To make this easier add a user preferences for
automatically selecting a base for merges. Let the default for this
new preference be 'First Parent', as this is what most users expect.

Change-Id: I633291f78fee7f9ce1feb73deb81f9312363b347
Signed-off-by: Edwin Kempin <ekempin@google.com>

Documentation/intro-user.txt

@@ -644,6 +644,23 @@ on comments that you write yourself.
 +
 Email notifications are disabled.
 
+- [[default-base-for-merges]]`Default Base For Merges`:
++
+This setting controls which base should be pre-selected in the
+`Diff Against` drop-down list when the change screen is opened for a
+merge commit.
++
+** `Auto Merge`:
++
+Pre-selects `Auto Merge` in the `Diff Against` drop-down list when the
+change screen is opened for a merge commit.
++
+** `First Parent`:
++
+Pre-selects `Parent 1` in the `Diff Against` drop-down list when the
+change screen is opened for a merge commit.
++
+
 - [[diff-view]]`Diff View`:
 +
 Whether the Side-by-Side diff view or the Unified diff view should be

Documentation/rest-api-accounts.txt

@@ -1213,6 +1213,7 @@ any account.
     "size_bar_in_change_table": true,
     "review_category_strategy": "ABBREV",
     "mute_common_path_prefixes": true,
+    "default_base_for_merges": "FIRST_PARENT",
     "my": [
       {
         "url": "#/dashboard/self",
@@ -2469,6 +2470,10 @@ from Gerrit. On `CC_ON_OWN_COMMENTS` the user will also receive emails for
 their own comments. On `DISABLED` the user will not receive any email
 notifications from Gerrit.
 Allowed values are `ENABLED`, `CC_ON_OWN_COMMENTS`, `DISABLED`.
+|`default_base_for_merges`      ||
+The base which should be pre-selected in the 'Diff Against' drop-down
+list when the change screen is opened for a merge commit.
+Allowed values are `AUTO_MERGE` and `FIRST_PARENT`.
 |============================================
 
 [[preferences-input]]
@@ -2527,6 +2532,10 @@ from Gerrit. On `CC_ON_OWN_COMMENTS` the user will also receive emails for
 their own comments. On `DISABLED` the user will not receive any email
 notifications from Gerrit.
 Allowed values are `ENABLED`, `CC_ON_OWN_COMMENTS`, `DISABLED`.
+|`default_base_for_merges`      |optional|
+The base which should be pre-selected in the 'Diff Against' drop-down
+list when the change screen is opened for a merge commit.
+Allowed values are `AUTO_MERGE` and `FIRST_PARENT`.
 |============================================
 
 [[query-limit-info]]

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/api/accounts/GeneralPreferencesIT.java

@@ -22,6 +22,7 @@ import com.google.gerrit.acceptance.NoHttpd;
 import com.google.gerrit.acceptance.TestAccount;
 import com.google.gerrit.extensions.client.GeneralPreferencesInfo;
 import com.google.gerrit.extensions.client.GeneralPreferencesInfo.DateFormat;
+import com.google.gerrit.extensions.client.GeneralPreferencesInfo.DefaultBase;
 import com.google.gerrit.extensions.client.GeneralPreferencesInfo.DiffView;
 import com.google.gerrit.extensions.client.GeneralPreferencesInfo.DownloadCommand;
 import com.google.gerrit.extensions.client.GeneralPreferencesInfo.EmailStrategy;
@@ -87,6 +88,7 @@ public class GeneralPreferencesIT extends AbstractDaemonTest {
     i.dateFormat = DateFormat.US;
     i.timeFormat = TimeFormat.HHMM_24;
     i.emailStrategy = EmailStrategy.DISABLED;
+    i.defaultBaseForMerges = DefaultBase.AUTO_MERGE;
     i.relativeDateInChangeTable ^= true;
     i.sizeBarInChangeTable ^= true;
     i.legacycidInChangeTable ^= true;

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/client/GeneralPreferencesInfo.java

@@ -83,6 +83,25 @@ public class GeneralPreferencesInfo {
     DISABLED
   }
 
+  public enum DefaultBase {
+    AUTO_MERGE(null),
+    FIRST_PARENT(-1);
+
+    private final String base;
+
+    DefaultBase(String base) {
+      this.base = base;
+    }
+
+    DefaultBase(int base) {
+      this(Integer.toString(base));
+    }
+
+    public String getBase() {
+      return base;
+    }
+  }
+
   public enum TimeFormat {
     /** 12-hour clock: 1:15 am, 2:13 pm */
     HHMM_12("h:mm a"),
@@ -123,6 +142,7 @@ public class GeneralPreferencesInfo {
   public List<MenuItem> my;
   public Map<String, String> urlAliases;
   public EmailStrategy emailStrategy;
+  public DefaultBase defaultBaseForMerges;
 
   public boolean isShowInfoInReviewCategory() {
     return getReviewCategoryStrategy() != ReviewCategoryStrategy.NONE;
@@ -180,6 +200,7 @@ public class GeneralPreferencesInfo {
     p.legacycidInChangeTable = false;
     p.muteCommonPathPrefixes = true;
     p.signedOffBy = false;
+    p.defaultBaseForMerges = DefaultBase.FIRST_PARENT;
     return p;
   }
 }

gerrit-gwtui-common/src/main/java/com/google/gerrit/client/info/GeneralPreferences.java

@@ -19,6 +19,7 @@ import com.google.gerrit.client.rpc.NativeString;
 import com.google.gerrit.client.rpc.Natives;
 import com.google.gerrit.extensions.client.GeneralPreferencesInfo;
 import com.google.gerrit.extensions.client.GeneralPreferencesInfo.DateFormat;
+import com.google.gerrit.extensions.client.GeneralPreferencesInfo.DefaultBase;
 import com.google.gerrit.extensions.client.GeneralPreferencesInfo.DiffView;
 import com.google.gerrit.extensions.client.GeneralPreferencesInfo.DownloadCommand;
 import com.google.gerrit.extensions.client.GeneralPreferencesInfo.EmailStrategy;
@@ -55,6 +56,7 @@ public class GeneralPreferences extends JavaScriptObject {
     p.reviewCategoryStrategy(d.getReviewCategoryStrategy());
     p.diffView(d.getDiffView());
     p.emailStrategy(d.emailStrategy);
+    p.defaultBaseForMerges(d.defaultBaseForMerges);
     return p;
   }
 
@@ -135,6 +137,14 @@ public class GeneralPreferences extends JavaScriptObject {
   private native String emailStrategyRaw()
   /*-{ return this.email_strategy }-*/;
 
+  public final DefaultBase defaultBaseForMerges() {
+    String s = defaultBaseForMergesRaw();
+    return s != null ? DefaultBase.valueOf(s) : null;
+  }
+
+  private native String defaultBaseForMergesRaw()
+  /*-{ return this.default_base_for_merges }-*/;
+
   public final native JsArray<TopMenuItem> my()
   /*-{ return this.my; }-*/;
 
@@ -201,6 +211,12 @@ public class GeneralPreferences extends JavaScriptObject {
   private native void emailStrategyRaw(String s)
   /*-{ this.email_strategy = s }-*/;
 
+  public final void defaultBaseForMerges(DefaultBase b) {
+    defaultBaseForMergesRaw(b != null ? b.toString() : null);
+  }
+  private native void defaultBaseForMergesRaw(String b)
+  /*-{ this.default_base_for_merges = b }-*/;
+
   public final void setMyMenus(List<TopMenuItem> myMenus) {
     initMy();
     for (TopMenuItem n : myMenus) {

gerrit-gwtui/src/main/java/com/google/gerrit/client/account/AccountConstants.java

@@ -168,4 +168,8 @@ public interface AccountConstants extends Constants {
   String messageCCMeOnMyComments();
   String messageDisabled();
   String emailFieldLabel();
+
+  String defaultBaseForMerges();
+  String autoMerge();
+  String firstParent();
 }

gerrit-gwtui/src/main/java/com/google/gerrit/client/account/AccountConstants.properties

@@ -19,6 +19,10 @@ messageEnabled = Enabled
 messageCCMeOnMyComments = CC Me On Comments I Write
 messageDisabled = Disabled
 
+defaultBaseForMerges = Default Base For Merges:
+autoMerge = Auto Merge
+firstParent = First Parent
+
 maximumPageSizeFieldLabel = Maximum Page Size:
 diffViewLabel = Diff View:
 dateFormatLabel = Date/Time Format:

gerrit-gwtui/src/main/java/com/google/gerrit/client/account/MyPreferencesScreen.java

@@ -61,6 +61,7 @@ public class MyPreferencesScreen extends SettingsScreen {
   private ListBox reviewCategoryStrategy;
   private ListBox diffView;
   private ListBox emailStrategy;
+  private ListBox defaultBaseForMerges;
   private StringListPanel myMenus;
   private Button save;
 
@@ -106,6 +107,12 @@ public class MyPreferencesScreen extends SettingsScreen {
             GeneralPreferencesInfo.EmailStrategy.DISABLED
                 .name());
 
+    defaultBaseForMerges = new ListBox();
+    defaultBaseForMerges.addItem(Util.C.autoMerge(),
+        GeneralPreferencesInfo.DefaultBase.AUTO_MERGE.name());
+    defaultBaseForMerges.addItem(Util.C.firstParent(),
+        GeneralPreferencesInfo.DefaultBase.FIRST_PARENT.name());
+
     diffView = new ListBox();
     diffView.addItem(
         com.google.gerrit.client.changes.Util.C.sideBySide(),
@@ -156,7 +163,7 @@ public class MyPreferencesScreen extends SettingsScreen {
     signedOffBy = new CheckBox(Util.C.signedOffBy());
 
     boolean flashClippy = !UserAgent.hasJavaScriptClipboard() && UserAgent.Flash.isInstalled();
-    final Grid formGrid = new Grid(12 + (flashClippy ? 1 : 0), 2);
+    final Grid formGrid = new Grid(13 + (flashClippy ? 1 : 0), 2);
 
     int row = 0;
 
@@ -176,6 +183,10 @@ public class MyPreferencesScreen extends SettingsScreen {
     formGrid.setWidget(row, fieldIdx, emailStrategy);
     row++;
 
+    formGrid.setText(row, labelIdx, Util.C.defaultBaseForMerges());
+    formGrid.setWidget(row, fieldIdx, defaultBaseForMerges);
+    row++;
+
     formGrid.setText(row, labelIdx, Util.C.diffViewLabel());
     formGrid.setWidget(row, fieldIdx, diffView);
     row++;
@@ -239,6 +250,7 @@ public class MyPreferencesScreen extends SettingsScreen {
     e.listenTo(diffView);
     e.listenTo(reviewCategoryStrategy);
     e.listenTo(emailStrategy);
+    e.listenTo(defaultBaseForMerges);
   }
 
   @Override
@@ -272,6 +284,7 @@ public class MyPreferencesScreen extends SettingsScreen {
     reviewCategoryStrategy.setEnabled(on);
     diffView.setEnabled(on);
     emailStrategy.setEnabled(on);
+    defaultBaseForMerges.setEnabled(on);
   }
 
   private void display(GeneralPreferences p) {
@@ -296,6 +309,9 @@ public class MyPreferencesScreen extends SettingsScreen {
     setListBox(emailStrategy,
         GeneralPreferencesInfo.EmailStrategy.ENABLED,
         p.emailStrategy());
+    setListBox(defaultBaseForMerges,
+        GeneralPreferencesInfo.DefaultBase.FIRST_PARENT,
+        p.defaultBaseForMerges());
     display(p.my());
   }
 
@@ -385,6 +401,10 @@ public class MyPreferencesScreen extends SettingsScreen {
         GeneralPreferencesInfo.EmailStrategy.ENABLED,
         GeneralPreferencesInfo.EmailStrategy.values()));
 
+    p.defaultBaseForMerges(getListBox(defaultBaseForMerges,
+        GeneralPreferencesInfo.DefaultBase.FIRST_PARENT,
+        GeneralPreferencesInfo.DefaultBase.values()));
+
     List<TopMenuItem> items = new ArrayList<>();
     for (List<String> v : myMenus.getValues()) {
       items.add(TopMenuItem.create(v.get(0), v.get(1)));

gerrit-gwtui/src/main/java/com/google/gerrit/client/change/ChangeScreen.java

@@ -287,13 +287,17 @@ public class ChangeScreen extends Screen {
             info.init();
             addExtensionPoints(info, initCurrentRevision(info));
 
-            RevisionInfo rev = info.revision(revision);
+            final RevisionInfo rev = info.revision(revision);
             CallbackGroup group = new CallbackGroup();
             loadCommit(rev, group);
 
             group.addListener(new GerritCallback<Void>() {
               @Override
               public void onSuccess(Void result) {
+                if (base == null && rev.commit().parents().length() > 1) {
+                  base = Gerrit.getUserPreferences()
+                      .defaultBaseForMerges().getBase();
+                }
                 loadConfigInfo(info, base);
               }
             });

gerrit-server/src/main/java/com/google/gerrit/server/schema/Schema_119.java

@@ -136,6 +136,8 @@ public class Schema_119 extends SchemaVersion {
           p.reviewCategoryStrategy =
               toReviewCategoryStrategy(rs.getString(14));
           p.muteCommonPathPrefixes = toBoolean(rs.getString(15));
+          p.defaultBaseForMerges =
+              GeneralPreferencesInfo.defaults().defaultBaseForMerges;
           imports.put(accountId, p);
         }
     }