Add built-in LFS smudge filter for local case

Adds a JGit built-in implementation of the "git lfs smudge" filter. This
filter should do the same as the one described in [1] besides that it
only supports the local case when the lfs objects are already present in
the media directory. Remote cases where download of LFS objects from an
LFS server is needed will be done in a later commit.

[1] https://github.com/github/git-lfs/blob/master/docs/man/git-lfs-smudge.1.ronn

Change-Id: I8ff661d4edd3667ef7f86f3b4fa33e568eb4c8f4

3 files changed, 179 insertions, 1 deletions

diff --git a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/LfsPointer.java b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/LfsPointer.java
index 2521e63163..e43cb2563b 100644
--- a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/LfsPointer.java
+++ b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/LfsPointer.java
@@ -42,9 +42,14 @@
  */
 package org.eclipse.jgit.lfs;
 
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
 import java.io.OutputStream;
 import java.io.PrintStream;
 
+import org.eclipse.jgit.annotations.Nullable;
 import org.eclipse.jgit.lfs.lib.Constants;
 import org.eclipse.jgit.lfs.lib.LongObjectId;
 
@@ -113,9 +118,50 @@ public class LfsPointer {
 		}
 	}
 
+	/**
+	 * Try to parse the data provided by an InputStream to the format defined by
+	 * {@link #VERSION}
+	 *
+	 * @param in
+	 *            the {@link InputStream} from where to read the data
+	 * @return an {@link LfsPointer} or <code>null</code> if the stream was not
+	 *         parseable as LfsPointer
+	 * @throws IOException
+	 */
+	@Nullable
+	public static LfsPointer parseLfsPointer(InputStream in)
+			throws IOException {
+		boolean versionLine = false;
+		LongObjectId id = null;
+		long sz = -1;
+
+		try (BufferedReader br = new BufferedReader(
+				new InputStreamReader(in))) {
+			for (String s = br.readLine(); s != null; s = br.readLine()) {
+				if (s.startsWith("#") || s.length() == 0) { //$NON-NLS-1$
+					continue;
+				} else if (s.startsWith("version") && s.length() > 8 //$NON-NLS-1$
+						&& s.substring(8).trim().equals(VERSION)) {
+					versionLine = true;
+				} else if (s.startsWith("oid sha256:")) { //$NON-NLS-1$
+					id = LongObjectId.fromString(s.substring(11).trim());
+				} else if (s.startsWith("size") && s.length() > 5) { //$NON-NLS-1$
+					sz = Long.parseLong(s.substring(5).trim());
+				} else {
+					return null;
+				}
+			}
+			if (versionLine && id != null && sz > -1) {
+				return new LfsPointer(id, sz);
+			}
+		}
+		return null;
+	}
+
 	@Override
 	public String toString() {
 		return "LfsPointer: oid=" + LongObjectId.toString(oid) + ", size=" //$NON-NLS-1$ //$NON-NLS-2$
 				+ size;
 	}
-}
\ No newline at end of file
+}
+
diff --git a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/SmudgeFilter.java b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/SmudgeFilter.java
new file mode 100644
index 0000000000..233247779d
--- /dev/null
+++ b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/SmudgeFilter.java
@@ -0,0 +1,125 @@
+/*
+ * Copyright (C) 2016, Christian Halstrick <christian.halstrick@sap.com>
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package org.eclipse.jgit.lfs;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import org.eclipse.jgit.attributes.FilterCommand;
+import org.eclipse.jgit.attributes.FilterCommandFactory;
+import org.eclipse.jgit.attributes.FilterCommandRegistry;
+import org.eclipse.jgit.lfs.lib.Constants;
+import org.eclipse.jgit.lib.Repository;
+
+/**
+ * Built-in LFS smudge filter
+ *
+ * When content is read from git's object-database and written to the filesystem
+ * and this filter is configured for that content, then this filter will replace
+ * the content of LFS pointer files with the original content. This happens e.g.
+ * when a checkout needs to update a working tree file which is under LFS
+ * control. This implementation expects that the origin content is already
+ * available in the .git/lfs/objects folder. This implementation will not
+ * contact any LFS servers in order to get the missing content.
+ *
+ * @since 4.6
+ */
+public class SmudgeFilter extends FilterCommand {
+	/**
+	 * The factory is responsible for creating instances of {@link SmudgeFilter}
+	 */
+	public final static FilterCommandFactory FACTORY = new FilterCommandFactory() {
+		@Override
+		public FilterCommand create(Repository db, InputStream in,
+				OutputStream out) throws IOException {
+			return new SmudgeFilter(db, in, out);
+		}
+	};
+
+	/**
+	 * Registers this filter in JGit by calling
+	 */
+	public final static void register() {
+		FilterCommandRegistry.register(
+				org.eclipse.jgit.lib.Constants.BUILTIN_FILTER_PREFIX
+						+ "lfs/smudge", //$NON-NLS-1$
+				FACTORY);
+	}
+
+	private Lfs lfs;
+
+	/**
+	 * @param db
+	 * @param in
+	 * @param out
+	 * @throws IOException
+	 */
+	public SmudgeFilter(Repository db, InputStream in, OutputStream out)
+			throws IOException {
+		super(in, out);
+		lfs = new Lfs(db.getDirectory().toPath().resolve(Constants.LFS));
+		LfsPointer res = LfsPointer.parseLfsPointer(in);
+		if (res != null) {
+			Path mediaFile = lfs.getMediaFile(res.getOid());
+			if (Files.exists(mediaFile)) {
+				this.in = Files.newInputStream(mediaFile);
+			}
+		}
+	}
+
+	@Override
+	public int run() throws IOException {
+		int b;
+		if (in != null) {
+			while ((b = in.read()) != -1) {
+				out.write(b);
+			}
+			in.close();
+		}
+		out.close();
+		return -1;
+	}
+}
diff --git a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/Constants.java b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/Constants.java
index 269cbc3a83..20e87ae0b9 100644
--- a/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/Constants.java
+++ b/org.eclipse.jgit.lfs/src/org/eclipse/jgit/lfs/lib/Constants.java
@@ -56,6 +56,13 @@ import org.eclipse.jgit.lfs.internal.LfsText;
 @SuppressWarnings("nls")
 public final class Constants {
 	/**
+	 * lfs folder
+	 *
+	 * @since 4.6
+	 */
+	public static final String LFS = "lfs";
+
+	/**
 	 * Hash function used natively by Git LFS extension for large objects.
 	 *
 	 * @since 4.6