[JGIT PATCH 5/8] Allow CanonicalTreeParsers to be created with a UTF-8 path prefix

["Shawn O. Pearce" <spearce@spearce.org>]

Creating an iterator with a path prefix permits a tree to be
"mounted" at a different part of a repository, permitting more
sophisticated merge strategies beyond just 1:1 path matching.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
---
 .../jgit/treewalk/AbstractTreeIterator.java        |   31 ++++++++++++++++++++
 .../spearce/jgit/treewalk/CanonicalTreeParser.java |   28 ++++++++++++++++++
 .../src/org/spearce/jgit/treewalk/TreeWalk.java    |    2 +-
 3 files changed, 60 insertions(+), 1 deletions(-)

diff --git a/org.spearce.jgit/src/org/spearce/jgit/treewalk/AbstractTreeIterator.java b/org.spearce.jgit/src/org/spearce/jgit/treewalk/AbstractTreeIterator.java
index 5226ab6..adfbb11 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/treewalk/AbstractTreeIterator.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/treewalk/AbstractTreeIterator.java
@@ -170,6 +170,37 @@ protected AbstractTreeIterator(final String prefix) {
 	}
 
 	/**
+	 * Create a new iterator with no parent and a prefix.
+	 * <p>
+	 * The prefix path supplied is inserted in front of all paths generated by
+	 * this iterator. It is intended to be used when an iterator is being
+	 * created for a subsection of an overall repository and needs to be
+	 * combined with other iterators that are created to run over the entire
+	 * repository namespace.
+	 *
+	 * @param prefix
+	 *            position of this iterator in the repository tree. The value
+	 *            may be null or the empty array to indicate the prefix is the
+	 *            root of the repository. A trailing slash ('/') is
+	 *            automatically appended if the prefix does not end in '/'.
+	 */
+	protected AbstractTreeIterator(final byte[] prefix) {
+		parent = null;
+
+		if (prefix != null && prefix.length > 0) {
+			pathLen = prefix.length;
+			path = new byte[Math.max(DEFAULT_PATH_SIZE, pathLen + 1)];
+			System.arraycopy(prefix, 0, path, 0, pathLen);
+			if (path[pathLen - 1] != '/')
+				path[pathLen++] = '/';
+			pathOffset = pathLen;
+		} else {
+			path = new byte[DEFAULT_PATH_SIZE];
+			pathOffset = 0;
+		}
+	}
+	
+	/**
 	 * Create an iterator for a subtree of an existing iterator.
 	 * 
 	 * @param p
diff --git a/org.spearce.jgit/src/org/spearce/jgit/treewalk/CanonicalTreeParser.java b/org.spearce.jgit/src/org/spearce/jgit/treewalk/CanonicalTreeParser.java
index dcc53cd..3dac6dd 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/treewalk/CanonicalTreeParser.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/treewalk/CanonicalTreeParser.java
@@ -62,6 +62,34 @@ public CanonicalTreeParser() {
 		// Nothing necessary.
 	}
 
+	/**
+	 * Create a new parser for a tree appearing in a subset of a repository.
+	 * 
+	 * @param prefix
+	 *            position of this iterator in the repository tree. The value
+	 *            may be null or the empty array to indicate the prefix is the
+	 *            root of the repository. A trailing slash ('/') is
+	 *            automatically appended if the prefix does not end in '/'.
+	 * @param repo
+	 *            repository to load the tree data from.
+	 * @param treeId
+	 *            identity of the tree being parsed; used only in exception
+	 *            messages if data corruption is found.
+	 * @throws MissingObjectException
+	 *             the object supplied is not available from the repository.
+	 * @throws IncorrectObjectTypeException
+	 *             the object supplied as an argument is not actually a tree and
+	 *             cannot be parsed as though it were a tree.
+	 * @throws IOException
+	 *             a loose object or pack file could not be read.
+	 */
+	public CanonicalTreeParser(final byte[] prefix, final Repository repo,
+			final ObjectId treeId) throws IncorrectObjectTypeException,
+			IOException {
+		super(prefix);
+		reset(repo, treeId);
+	}
+
 	private CanonicalTreeParser(final CanonicalTreeParser p) {
 		super(p);
 	}
diff --git a/org.spearce.jgit/src/org/spearce/jgit/treewalk/TreeWalk.java b/org.spearce.jgit/src/org/spearce/jgit/treewalk/TreeWalk.java
index 3af3d09..b1cbd2d 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/treewalk/TreeWalk.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/treewalk/TreeWalk.java
@@ -307,7 +307,7 @@ public void reset(final ObjectId[] ids) throws MissingObjectException,
 				o = trees[i];
 				while (o.parent != null)
 					o = o.parent;
-				if (o instanceof CanonicalTreeParser) {
+				if (o instanceof CanonicalTreeParser && o.pathOffset == 0) {
 					o.matches = null;
 					o.matchShift = 0;
 					((CanonicalTreeParser) o).reset(db, ids[i]);
-- 
1.6.0.2.706.g340fc