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/*
* Copyright (C) 2006-2008, Shawn O. Pearce <spearce@spearce.org>
* 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.lib;
/**
* Pairing of a name and the {@link ObjectId} it currently has.
* <p>
* A ref in Git is (more or less) a variable that holds a single object
* identifier. The object identifier can be any valid Git object (blob, tree,
* commit, annotated tag, ...).
* <p>
* The ref name has the attributes of the ref that was asked for as well as the
* ref it was resolved to for symbolic refs plus the object id it points to and
* (for tags) the peeled target object id, i.e. the tag resolved recursively
* until a non-tag object is referenced.
*/
public interface Ref {
/** Location where a {@link Ref} is stored. */
public static enum Storage {
/**
* The ref does not exist yet, updating it may create it.
* <p>
* Creation is likely to choose {@link #LOOSE} storage.
*/
NEW(true, false),
/**
* The ref is stored in a file by itself.
* <p>
* Updating this ref affects only this ref.
*/
LOOSE(true, false),
/**
* The ref is stored in the <code>packed-refs</code> file, with others.
* <p>
* Updating this ref requires rewriting the file, with perhaps many
* other refs being included at the same time.
*/
PACKED(false, true),
/**
* The ref is both {@link #LOOSE} and {@link #PACKED}.
* <p>
* Updating this ref requires only updating the loose file, but deletion
* requires updating both the loose file and the packed refs file.
*/
LOOSE_PACKED(true, true),
/**
* The ref came from a network advertisement and storage is unknown.
* <p>
* This ref cannot be updated without Git-aware support on the remote
* side, as Git-aware code consolidate the remote refs and reported them
* to this process.
*/
NETWORK(false, false);
private final boolean loose;
private final boolean packed;
private Storage(final boolean l, final boolean p) {
loose = l;
packed = p;
}
/**
* @return true if this storage has a loose file.
*/
public boolean isLoose() {
return loose;
}
/**
* @return true if this storage is inside the packed file.
*/
public boolean isPacked() {
return packed;
}
}
/**
* What this ref is called within the repository.
*
* @return name of this ref.
*/
public String getName();
/**
* Test if this reference is a symbolic reference.
* <p>
* A symbolic reference does not have its own {@link ObjectId} value, but
* instead points to another {@code Ref} in the same database and always
* uses that other reference's value as its own.
*
* @return true if this is a symbolic reference; false if this reference
* contains its own ObjectId.
*/
public abstract boolean isSymbolic();
/**
* Traverse target references until {@link #isSymbolic()} is false.
* <p>
* If {@link #isSymbolic()} is false, returns {@code this}.
* <p>
* If {@link #isSymbolic()} is true, this method recursively traverses
* {@link #getTarget()} until {@link #isSymbolic()} returns false.
* <p>
* This method is effectively
*
* <pre>
* return isSymbolic() ? getTarget().getLeaf() : this;
* </pre>
*
* @return the reference that actually stores the ObjectId value.
*/
public abstract Ref getLeaf();
/**
* Get the reference this reference points to, or {@code this}.
* <p>
* If {@link #isSymbolic()} is true this method returns the reference it
* directly names, which might not be the leaf reference, but could be
* another symbolic reference.
* <p>
* If this is a leaf level reference that contains its own ObjectId,this
* method returns {@code this}.
*
* @return the target reference, or {@code this}.
*/
public abstract Ref getTarget();
/**
* Cached value of this ref.
*
* @return the value of this ref at the last time we read it.
*/
public abstract ObjectId getObjectId();
/**
* Cached value of <code>ref^{}</code> (the ref peeled to commit).
*
* @return if this ref is an annotated tag the id of the commit (or tree or
* blob) that the annotated tag refers to; null if this ref does not
* refer to an annotated tag.
*/
public abstract ObjectId getPeeledObjectId();
/**
* @return whether the Ref represents a peeled tag
*/
public abstract boolean isPeeled();
/**
* How was this ref obtained?
* <p>
* The current storage model of a Ref may influence how the ref must be
* updated or deleted from the repository.
*
* @return type of ref.
*/
public abstract Storage getStorage();
}
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