Added one-tree constructor to DirCacheCheckout

When DirCacheCheckout should be used to checkout only one
tree (reset --hard, clone) then we had to use the standard
constructor and specify null as value for head. This change
adds explicit constructors not taking HEAD and documents
that.

Bug: 330021
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>

org.eclipse.jgit/src/org/eclipse/jgit/dircache/DirCacheCheckout.java

@@ -144,8 +144,8 @@ public class DirCacheCheckout {
 	}
 
 	/**
-	 * Constructs a DirCacheCeckout for fast-forwarding from one tree to
-	 * another, merging it with the index
+	 * Constructs a DirCacheCeckout for merging and checking out two trees (HEAD
+	 * and mergeCommitTree) and the index.
 	 *
 	 * @param repo
 	 *            the repository in which we do the checkout
@@ -169,6 +169,48 @@ public class DirCacheCheckout {
 		this.workingTree = workingTree;
 	}
 
+	/**
+	 * Constructs a DirCacheCeckout for merging and checking out two trees (HEAD
+	 * and mergeCommitTree) and the index. As iterator over the working tree
+	 * this constructor creates a standard {@link FileTreeIterator}
+	 *
+	 * @param repo
+	 *            the repository in which we do the checkout
+	 * @param headCommitTree
+	 *            the id of the tree of the head commit
+	 * @param dc
+	 *            the (already locked) Dircache for this repo
+	 * @param mergeCommitTree
+	 *            the id of the tree of the
+	 * @throws IOException
+	 */
+	public DirCacheCheckout(Repository repo, ObjectId headCommitTree,
+			DirCache dc, ObjectId mergeCommitTree) throws IOException {
+		this(repo, headCommitTree, dc, mergeCommitTree, new FileTreeIterator(
+				repo.getWorkTree(), repo.getFS(),
+				WorkingTreeOptions.createDefaultInstance()));
+	}
+
+	/**
+	 * Constructs a DirCacheCeckout for checking out one tree, merging with the
+	 * index.
+	 *
+	 * @param repo
+	 *            the repository in which we do the checkout
+	 * @param dc
+	 *            the (already locked) Dircache for this repo
+	 * @param mergeCommitTree
+	 *            the id of the tree we want to fast-forward to
+	 * @param workingTree
+	 *            an iterator over the repositories Working Tree
+	 * @throws IOException
+	 */
+	public DirCacheCheckout(Repository repo, DirCache dc,
+			ObjectId mergeCommitTree, WorkingTreeIterator workingTree)
+			throws IOException {
+		this(repo, null, dc, mergeCommitTree, workingTree);
+	}
+
 	/**
 	 * Constructs a DirCacheCeckout for checking out one tree, merging with the
 	 * index. As iterator over the working tree this constructor creates a
@@ -176,17 +218,15 @@ public class DirCacheCheckout {
 	 *
 	 * @param repo
 	 *            the repository in which we do the checkout
-	 * @param headCommitTree
-	 *            the id of the tree of the head commit
 	 * @param dc
 	 *            the (already locked) Dircache for this repo
 	 * @param mergeCommitTree
 	 *            the id of the tree of the
 	 * @throws IOException
 	 */
-	public DirCacheCheckout(Repository repo, ObjectId headCommitTree, DirCache dc,
+	public DirCacheCheckout(Repository repo, DirCache dc,
 			ObjectId mergeCommitTree) throws IOException {
-		this(repo, headCommitTree, dc, mergeCommitTree, new FileTreeIterator(
+		this(repo, null, dc, mergeCommitTree, new FileTreeIterator(
 				repo.getWorkTree(), repo.getFS(),
 				WorkingTreeOptions.createDefaultInstance()));
 	}