Add ConfigSubject over JGit Configs

The general pattern for check methods is Config#getFoo becomes
ConfigSubject#fooValues, with the same argument list. A more fluent API
using intermediate types may be possible, but the goal to start with is
to keep the API close to the underlying Config APIs.

Change-Id: I09e6e04a5a77fd440ff34d3d284b1d69f8440695

java/com/google/gerrit/truth/BUILD

@@ -6,6 +6,7 @@ java_library(
     deps = [
         "//java/com/google/gerrit/common:annotations",
         "//lib:guava",
+        "//lib/jgit/org.eclipse.jgit:jgit",
         "//lib/truth",
     ],
 )

java/com/google/gerrit/truth/ConfigSubject.java

@@ -0,0 +1,129 @@
+// Copyright (C) 2019 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.truth;
+
+import static com.google.common.truth.Truth.assertAbout;
+import static java.util.Objects.requireNonNull;
+
+import com.google.common.collect.ImmutableListMultimap;
+import com.google.common.truth.BooleanSubject;
+import com.google.common.truth.FailureMetadata;
+import com.google.common.truth.IntegerSubject;
+import com.google.common.truth.IterableSubject;
+import com.google.common.truth.ListMultimapSubject;
+import com.google.common.truth.LongSubject;
+import com.google.common.truth.StringSubject;
+import com.google.common.truth.Subject;
+import com.google.gerrit.common.Nullable;
+import java.util.Arrays;
+import org.eclipse.jgit.lib.Config;
+
+public class ConfigSubject extends Subject<ConfigSubject, Config> {
+  public static ConfigSubject assertThat(Config config) {
+    return assertAbout(ConfigSubject::new).that(config);
+  }
+
+  private final Config config;
+
+  private ConfigSubject(FailureMetadata metadata, Config actual) {
+    super(metadata, actual);
+    this.config = actual;
+  }
+
+  public IterableSubject sections() {
+    isNotNull();
+    return check("getSections()").that(config.getSections());
+  }
+
+  public IterableSubject subsections(String section) {
+    requireNonNull(section);
+    isNotNull();
+    return check("getSubsections(%s)", section).that(config.getSubsections(section));
+  }
+
+  public ListMultimapSubject sectionValues(String section) {
+    requireNonNull(section);
+    return sectionValuesImpl(section, null);
+  }
+
+  public ListMultimapSubject subsectionValues(String section, String subsection) {
+    requireNonNull(section);
+    requireNonNull(subsection);
+    return sectionValuesImpl(section, subsection);
+  }
+
+  private ListMultimapSubject sectionValuesImpl(String section, @Nullable String subsection) {
+    isNotNull();
+    ImmutableListMultimap.Builder<String, String> b = ImmutableListMultimap.builder();
+    config
+        .getNames(section, subsection, true)
+        .forEach(
+            n ->
+                Arrays.stream(config.getStringList(section, subsection, n))
+                    .forEach(v -> b.put(n, v)));
+    return check("getSection(%s, %s)", section, subsection).that(b.build());
+  }
+
+  public void isEmpty() {
+    sections().isEmpty();
+  }
+
+  public StringSubject text() {
+    isNotNull();
+    return check("toText()").that(config.toText());
+  }
+
+  public IterableSubject stringValues(String section, @Nullable String subsection, String name) {
+    requireNonNull(section);
+    requireNonNull(name);
+    isNotNull();
+    return check("getStringList(%s, %s, %s)", section, subsection, name)
+        .that(Arrays.asList(config.getStringList(section, subsection, name)));
+  }
+
+  public StringSubject stringValue(String section, @Nullable String subsection, String name) {
+    requireNonNull(section);
+    requireNonNull(name);
+    isNotNull();
+    return check("getString(%s, %s, %s)", section, subsection, name)
+        .that(config.getString(section, subsection, name));
+  }
+
+  public IntegerSubject intValue(
+      String section, @Nullable String subsection, String name, int defaultValue) {
+    requireNonNull(section);
+    requireNonNull(name);
+    isNotNull();
+    return check("getInt(%s, %s, %s, %s)", section, subsection, name, defaultValue)
+        .that(config.getInt(section, subsection, name, defaultValue));
+  }
+
+  public LongSubject longValue(String section, String subsection, String name, long defaultValue) {
+    requireNonNull(section);
+    requireNonNull(name);
+    isNotNull();
+    return check("getLong(%s, %s, %s, %s)", section, subsection, name, defaultValue)
+        .that(config.getLong(section, subsection, name, defaultValue));
+  }
+
+  public BooleanSubject booleanValue(
+      String section, String subsection, String name, boolean defaultValue) {
+    requireNonNull(section);
+    requireNonNull(name);
+    isNotNull();
+    return check("getBoolean(%s, %s, %s, %s)", section, subsection, name, defaultValue)
+        .that(config.getBoolean(section, subsection, name, defaultValue));
+  }
+}