WIP: Implement LFS plugin storing large objects in local file system

This plugin uses JGit's FileLfsRepository class to provide a local file
system based large file storage.

Large files are stored under the plugin's data directory
$GERRIT_SITE/plugins/lfs-storage-fs

This change makes use of the corresponding WIP in JGit [1]. Therefore,
to test locally you need to build JGit from [1] locally. In order to
make this plugin usable you must build Gerrit from [2] with this version
of JGit. This can be done using the multi-cell buck build introduced
in [3]. Follow the instructions given in [3] to build gerrit including
jgit.

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-fs

[1] https://git.eclipse.org/r/#/c/52177
[2] https://gerrit-review.googlesource.com/72891
[3] https://gerrit-review.googlesource.com/#/c/73000

Change-Id: Ic67c3586ec2dfdac614cc49d1e8582df624d74ef
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..db2011b
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,10 @@
+/target
+/.buckversion
+/.classpath
+/.settings
+/.project
+/.buckd
+/buck-cache
+/buck-out
+/bucklets
+/eclipse-out
\ No newline at end of file
diff --git a/BUCK b/BUCK
new file mode 100644
index 0000000..84561da
--- /dev/null
+++ b/BUCK
@@ -0,0 +1,58 @@
+include_defs('//lib/maven.defs')
+include_defs('//lib/JGIT_VERSION')
+
+gerrit_plugin(
+  name = 'lfs-storage-fs',
+  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-fs',
+    'Gerrit-HttpModule: com.googlesource.gerrit.plugins.lfslocal.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/lfslocal/HttpModule.java b/src/main/java/com/googlesource/gerrit/plugins/lfslocal/HttpModule.java
new file mode 100644
index 0000000..ee6b0b1
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/lfslocal/HttpModule.java
@@ -0,0 +1,29 @@
+// 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.lfslocal;
+
+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(LocalLargeFileRepository.class);
+
+    serve("/*").with(LfsContentServlet.class);
+  }
+}
diff --git a/src/main/java/com/googlesource/gerrit/plugins/lfslocal/LfsApiServlet.java b/src/main/java/com/googlesource/gerrit/plugins/lfslocal/LfsApiServlet.java
new file mode 100644
index 0000000..273db49
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/lfslocal/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.lfslocal;
+
+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 LocalLargeFileRepository repository;
+
+  @Inject
+  LfsApiServlet(LocalLargeFileRepository 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/lfslocal/LfsContentServlet.java b/src/main/java/com/googlesource/gerrit/plugins/lfslocal/LfsContentServlet.java
new file mode 100644
index 0000000..68c2831
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/lfslocal/LfsContentServlet.java
@@ -0,0 +1,30 @@
+// 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.lfslocal;
+
+import org.eclipse.jgit.lfs.server.fs.FileLfsServlet;
+
+import com.google.inject.Inject;
+import com.google.inject.Singleton;
+
+@Singleton
+public class LfsContentServlet extends FileLfsServlet {
+  private static final long serialVersionUID = 1L;
+
+  @Inject
+  LfsContentServlet(LocalLargeFileRepository largeFileRepository) {
+    super(largeFileRepository, 0);
+  }
+}
diff --git a/src/main/java/com/googlesource/gerrit/plugins/lfslocal/LocalLargeFileRepository.java b/src/main/java/com/googlesource/gerrit/plugins/lfslocal/LocalLargeFileRepository.java
new file mode 100644
index 0000000..41b3c14
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/lfslocal/LocalLargeFileRepository.java
@@ -0,0 +1,33 @@
+// 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.lfslocal;
+
+import java.io.IOException;
+import java.nio.file.Path;
+
+import org.eclipse.jgit.lfs.server.fs.FileLfsRepository;
+
+import com.google.gerrit.extensions.annotations.PluginCanonicalWebUrl;
+import com.google.gerrit.extensions.annotations.PluginData;
+import com.google.inject.Inject;
+
+public class LocalLargeFileRepository extends FileLfsRepository {
+
+  @Inject
+  LocalLargeFileRepository(@PluginCanonicalWebUrl String url,
+      @PluginData Path dataDir) throws IOException {
+    super(url, dataDir);
+  }
+}
diff --git a/src/main/resources/Documentation/about.md b/src/main/resources/Documentation/about.md
new file mode 100644
index 0000000..63e1cbb
--- /dev/null
+++ b/src/main/resources/Documentation/about.md
@@ -0,0 +1,4 @@
+This plugin provides a local file system storage for the LFS service.
+
+The large files are stored under the plugin's data directory
+$GERRIT_SITE/data/lfs-storage-fs.
diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
new file mode 100644
index 0000000..f44d0a4
--- /dev/null
+++ b/src/main/resources/Documentation/config.md
@@ -0,0 +1,4 @@
+@PLUGIN@ Configuration
+======================
+
+This plugin has no configuration.