WIP: Implement LFS plugin storing large objects in an Amazon S3 bucket

This plugin uses JGit's S3Repository class to provide a large file
storage using an Amazon S3 bucket.

The plugin supports only in-tree buck build. To build it clone the
repository under .../plugins folder and then execute:

$ buck build plugins/lfs-storage-s3

Change-Id: I635c1c5454a0b23a8e9f9fceab9743692f7c72cb
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..1d324ed
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+/.classpath
+/.project
+/.settings/org.maven.ide.eclipse.prefs
diff --git a/BUCK b/BUCK
new file mode 100644
index 0000000..147c902
--- /dev/null
+++ b/BUCK
@@ -0,0 +1,58 @@
+include_defs('//lib/maven.defs')
+include_defs('//lib/JGIT_VERSION')
+
+gerrit_plugin(
+  name = 'lfs-storage-s3',
+  srcs = glob(['src/main/java/**/*.java']),
+  resources = glob(['src/main/resources/**/*']),
+  deps = [
+    ':jgit-http-apache',
+    ':jgit-lfs',
+    ':jgit-lfs-server',
+  ],
+  manifest_entries = [
+    'Gerrit-PluginName: lfs-storage-s3',
+    'Gerrit-HttpModule: com.googlesource.gerrit.plugins.lfs.s3.HttpModule',
+  ],
+)
+
+maven_jar(
+  name = 'jgit-http-apache',
+  id = 'org.eclipse.jgit:org.eclipse.jgit.http.apache:' + VERS,
+  sha1 = '8a589f2c7a623d8fc5a38edbaf11af2061a2baea',
+  license = 'jgit',
+  repository = REPO,
+  unsign = True,
+  exclude = [
+    'about.html',
+    'plugin.properties',
+  ],
+)
+
+maven_jar(
+  name = 'jgit-lfs',
+  id = 'org.eclipse.jgit:org.eclipse.jgit.lfs:' + VERS,
+  bin_sha1 = '3ac14ac1fe71b9390183b9a41a749182556c5bf2',
+  src_sha1 = '4008b18150f71a4eb6da77882ef222ce86a8a469',
+  license = 'jgit',
+  repository = REPO,
+  unsign = True,
+  exclude = [
+    'about.html',
+    'plugin.properties',
+  ],
+)
+
+maven_jar(
+  name = 'jgit-lfs-server',
+  id = 'org.eclipse.jgit:org.eclipse.jgit.lfs.server:' + VERS,
+  bin_sha1 = '0eb4803d6fa08100a4bd8dfbac44ec21f870ceff',
+  src_sha1 = '95b1695aca8ec1b53f6ca17f3d3361f2c2ac71f3',
+  license = 'jgit',
+  repository = REPO,
+  unsign = True,
+  exclude = [
+    'about.html',
+    'plugin.properties',
+  ],
+)
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..11069ed
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,201 @@
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diff --git a/src/main/java/com/googlesource/gerrit/plugins/lfs/s3/HttpModule.java b/src/main/java/com/googlesource/gerrit/plugins/lfs/s3/HttpModule.java
new file mode 100644
index 0000000..c9999ca
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/lfs/s3/HttpModule.java
@@ -0,0 +1,28 @@
+// Copyright (C) 2016 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.googlesource.gerrit.plugins.lfs.s3;
+
+import static com.google.gerrit.httpd.plugins.LfsPluginServlet.URL_REGEX;
+
+import com.google.gerrit.httpd.plugins.HttpPluginModule;
+
+public class HttpModule extends HttpPluginModule {
+
+  @Override
+  protected void configureServlets() {
+    serveRegex(URL_REGEX).with(LfsApiServlet.class);
+    bind(S3LargeFileRepository.class);
+  }
+}
diff --git a/src/main/java/com/googlesource/gerrit/plugins/lfs/s3/LfsApiServlet.java b/src/main/java/com/googlesource/gerrit/plugins/lfs/s3/LfsApiServlet.java
new file mode 100644
index 0000000..985c663
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/lfs/s3/LfsApiServlet.java
@@ -0,0 +1,38 @@
+//Copyright (C) 2016 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.googlesource.gerrit.plugins.lfs.s3;
+
+import com.google.inject.Inject;
+import com.google.inject.Singleton;
+
+import org.eclipse.jgit.lfs.server.LargeFileRepository;
+import org.eclipse.jgit.lfs.server.LfsProtocolServlet;
+
+@Singleton
+public class LfsApiServlet extends LfsProtocolServlet {
+  private static final long serialVersionUID = 1L;
+
+  private final S3LargeFileRepository repository;
+
+  @Inject
+  LfsApiServlet(S3LargeFileRepository repository) {
+    this.repository = repository;
+  }
+
+  @Override
+  protected LargeFileRepository getLargeFileRepository() {
+    return repository;
+  }
+}
\ No newline at end of file
diff --git a/src/main/java/com/googlesource/gerrit/plugins/lfs/s3/S3LargeFileRepository.java b/src/main/java/com/googlesource/gerrit/plugins/lfs/s3/S3LargeFileRepository.java
new file mode 100644
index 0000000..c9da0f3
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/lfs/s3/S3LargeFileRepository.java
@@ -0,0 +1,46 @@
+// Copyright (C) 2015 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.googlesource.gerrit.plugins.lfs.s3;
+
+import com.google.gerrit.extensions.annotations.PluginName;
+import com.google.gerrit.server.config.PluginConfig;
+import com.google.gerrit.server.config.PluginConfigFactory;
+import com.google.inject.Inject;
+
+import org.eclipse.jgit.lfs.server.s3.S3Config;
+import org.eclipse.jgit.lfs.server.s3.S3Repository;
+
+public class S3LargeFileRepository extends S3Repository {
+
+  @Inject
+  S3LargeFileRepository(PluginConfigFactory cfg, @PluginName String pluginName) {
+    super(getS3Config(cfg, pluginName));
+  }
+
+  private static S3Config getS3Config(PluginConfigFactory configFactory,
+      String pluginName) {
+    PluginConfig cfg = configFactory.getFromGerritConfig(pluginName);
+    String region = cfg.getString("region", null);
+    String bucket = cfg.getString("bucket", null);
+    String storageClass = cfg.getString("storageClass", "REDUCED_REDUNDANCY");
+    String accessKey = cfg.getString("accessKey", null);
+    String secretKey = cfg.getString("secretKey", null);
+    int expirationSeconds = cfg.getInt("expirationSeconds", 60);
+    boolean disableSslVerify = cfg.getBoolean("disableSslVerify", false);
+
+    return new S3Config(region, bucket, storageClass, accessKey, secretKey,
+        expirationSeconds, disableSslVerify);
+  }
+}
diff --git a/src/main/resources/Documentation/about.md b/src/main/resources/Documentation/about.md
new file mode 100644
index 0000000..c379e0c
--- /dev/null
+++ b/src/main/resources/Documentation/about.md
@@ -0,0 +1 @@
+This plugin provides an Amazon S3 storage for the LFS service.
diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
new file mode 100644
index 0000000..8aa0ccf
--- /dev/null
+++ b/src/main/resources/Documentation/config.md
@@ -0,0 +1,55 @@
+@PLUGIN@ Configuration
+======================
+
+The following options can be configured in `etc/gerrit.config`
+
+[[plugin "lfs-storage-s3"]]
+=== Section plugin.lfs-storage-s3
+
+[[plugin.lfs-storage-s3.region]]plugin.lfs-storage-s3.region::
++
+link:http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-regions-availability-zones.html#concepts-available-regions
+[Amazon region] the S3 storage bucket is residing in.
+
+[[plugin.lfs-storage-s3.bucket]]plugin.lfs-storage-s3.bucket::
++
+Name of the link:http://docs.aws.amazon.com/AmazonS3/latest/UG/CreatingaBucket.html
+[Amazon S3 storage bucket] which will store large objects.
+
+[[plugin.lfs-storage-s3.storageClass]]plugin.lfs-storage-s3.storageClass::
++
+link:http://docs.aws.amazon.com/AmazonS3/latest/dev/storage-class-intro.html
+[Amazon S3 storage class] used for storing large objects.
++
+Default is `REDUCED_REDUNDANCY`
+
+[[plugin.lfs-storage-s3.expiration]]plugin.lfs-storage-s3.expiration::
++
+Expiration in seconds of validity of signed requests. Gerrit's LFS protocol
+handler signs requests to be issued by the git-lfs extension with the configured
+`accessKey` and `secretKey`. This way the git-lfs extension doesn't need
+any credentials to access objects in the S3 bucket. Validity of these request
+signatures expires after this period.
++
+Default is `60` seconds.
+
+[[plugin.lfs-storage-s3.disableSslVerify]]plugin.lfs-storage-s3.disableSslVerify::
++
+`true`: SSL verification is disabled
++
+`false`: SSL verification is enabled
++
+Default is `false`.
+
+----
+The following options can be configured in `etc/secure.config`
+
+[[plugin.lfs-storage-s3.accessKey]]plugin.lfs-storage-s3.accessKey::
++
+The link:http://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_access-keys.html
+[Amazon IAM accessKey] for authenticating to S3.
+
+[[plugin.lfs-storage-s3.secretKey]]plugin.lfs-storage-s3.secretKey::
++
+The link:http://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_access-keys.html
+[Amazon IAM secretKey] for authenticating to S3.