Implement Bazel build

This change adds two Bazel build modes:

1. Standalone build mode (Bazlets driven)
2. In Gerrit tree build mode

Bazlets repository is currently consumed from GH, but can be moved
later to gerrit-review.

TEST PLAN:

  1. run `bazel build reviewers` in reviewers project
  2. link reviewers directory to gerrit/plugins and run
     `bazel build plugins/reviewers` in gerrit tree

Change-Id: Ie60e32096a039f75402a202ff14556118b18d86f
diff --git a/.gitignore b/.gitignore
index aa42023..3245346 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,3 +10,8 @@
 *.pyc
 .buckversion
 /bucklets
+/bazel-bin
+/bazel-genfiles
+/bazel-out
+/bazel-reviewers
+/bazel-testlogs
diff --git a/BUILD b/BUILD
new file mode 100644
index 0000000..6086d5c
--- /dev/null
+++ b/BUILD
@@ -0,0 +1,12 @@
+load("//tools/bzl:plugin.bzl", "gerrit_plugin")
+
+gerrit_plugin(
+    name = "reviewers",
+    srcs = glob(["src/main/java/**/*.java"]),
+    gwt_module = "com.googlesource.gerrit.plugins.reviewers.ReviewersForm",
+    manifest_entries = [
+        "Gerrit-PluginName: reviewers",
+        "Gerrit-Module: com.googlesource.gerrit.plugins.reviewers.Module",
+    ],
+    resources = glob(["src/main/**/*"]),
+)
diff --git a/WORKSPACE b/WORKSPACE
new file mode 100644
index 0000000..5716471
--- /dev/null
+++ b/WORKSPACE
@@ -0,0 +1,30 @@
+workspace(name = "reviewers")
+
+load("//:bazlets.bzl", "load_bazlets")
+
+load_bazlets(
+    commit = "3bec81727c69207e591ae1761d5a78d8ec418a0b",
+    #    local_path = "/home/<user>/projects/bazlets",
+)
+
+# Release Plugin API
+#load("@com_googlesource_gerrit_bazlets//:gerrit_api.bzl",
+#     "gerrit_api")
+
+# Snapshot Plugin API
+load(
+    "@com_googlesource_gerrit_bazlets//:gerrit_api_maven_local.bzl",
+    "gerrit_api_maven_local",
+)
+load(
+    "@com_googlesource_gerrit_bazlets//:gerrit_gwt.bzl",
+    "gerrit_gwt",
+)
+
+# Load release Plugin API
+# gerrit_api()
+
+# Load snapshot Plugin API
+gerrit_api_maven_local()
+
+gerrit_gwt()
diff --git a/bazlets.bzl b/bazlets.bzl
new file mode 100644
index 0000000..e14e488
--- /dev/null
+++ b/bazlets.bzl
@@ -0,0 +1,17 @@
+NAME = "com_googlesource_gerrit_bazlets"
+
+def load_bazlets(
+    commit,
+    local_path = None
+  ):
+  if not local_path:
+      native.git_repository(
+          name = NAME,
+          remote = "https://gerrit.googlesource.com/bazlets",
+          commit = commit,
+      )
+  else:
+      native.local_repository(
+          name = NAME,
+          path = local_path,
+      )
diff --git a/tools/bazel.rc b/tools/bazel.rc
new file mode 100644
index 0000000..4ed16cf
--- /dev/null
+++ b/tools/bazel.rc
@@ -0,0 +1,2 @@
+build --workspace_status_command=./tools/workspace-status.sh
+test --build_tests_only
diff --git a/tools/bzl/BUILD b/tools/bzl/BUILD
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/tools/bzl/BUILD
diff --git a/tools/bzl/plugin.bzl b/tools/bzl/plugin.bzl
new file mode 100644
index 0000000..2b1df8c
--- /dev/null
+++ b/tools/bzl/plugin.bzl
@@ -0,0 +1,4 @@
+load(
+    "@com_googlesource_gerrit_bazlets//:gerrit_plugin.bzl",
+    "gerrit_plugin",
+)
diff --git a/tools/workspace-status.sh b/tools/workspace-status.sh
new file mode 100755
index 0000000..674faeb
--- /dev/null
+++ b/tools/workspace-status.sh
@@ -0,0 +1,17 @@
+#!/bin/bash
+
+# This script will be run by bazel when the build process starts to
+# generate key-value information that represents the status of the
+# workspace. The output should be like
+#
+# KEY1 VALUE1
+# KEY2 VALUE2
+#
+# If the script exits with non-zero code, it's considered as a failure
+# and the output will be discarded.
+
+function rev() {
+  cd $1; git describe --always --match "v[0-9].*" --dirty
+}
+
+echo STABLE_BUILD_REVIEWERS_LABEL $(rev .)