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/*
* Copyright (C) 2008-2009, Google Inc.
* Copyright (C) 2009, Matthias Sohn <matthias.sohn@sap.com>
* Copyright (C) 2012, Research In Motion Limited and others
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0 which is available at
* https://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.eclipse.jgit.merge;
import java.text.MessageFormat;
import java.util.HashMap;
import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.lib.Config;
import org.eclipse.jgit.lib.ObjectInserter;
import org.eclipse.jgit.lib.Repository;
/**
* A method of combining two or more trees together to form an output tree.
* <p>
* Different strategies may employ different techniques for deciding which paths
* (and ObjectIds) to carry from the input trees into the final output tree.
*/
public abstract class MergeStrategy {
/** Simple strategy that sets the output tree to the first input tree. */
public static final MergeStrategy OURS = new StrategyOneSided("ours", 0); //$NON-NLS-1$
/** Simple strategy that sets the output tree to the second input tree. */
public static final MergeStrategy THEIRS = new StrategyOneSided("theirs", 1); //$NON-NLS-1$
/** Simple strategy to merge paths, without simultaneous edits. */
public static final ThreeWayMergeStrategy SIMPLE_TWO_WAY_IN_CORE = new StrategySimpleTwoWayInCore();
/**
* Simple strategy to merge paths. It tries to merge also contents. Multiple
* merge bases are not supported
*/
public static final ThreeWayMergeStrategy RESOLVE = new StrategyResolve();
/**
* Recursive strategy to merge paths. It tries to merge also contents.
* Multiple merge bases are supported
* @since 3.0
*/
public static final ThreeWayMergeStrategy RECURSIVE = new StrategyRecursive();
private static final HashMap<String, MergeStrategy> STRATEGIES = new HashMap<>();
static {
register(OURS);
register(THEIRS);
register(SIMPLE_TWO_WAY_IN_CORE);
register(RESOLVE);
register(RECURSIVE);
}
/**
* Register a merge strategy so it can later be obtained by name.
*
* @param imp
* the strategy to register.
* @throws java.lang.IllegalArgumentException
* a strategy by the same name has already been registered.
*/
public static void register(MergeStrategy imp) {
register(imp.getName(), imp);
}
/**
* Register a merge strategy so it can later be obtained by name.
*
* @param name
* name the strategy can be looked up under.
* @param imp
* the strategy to register.
* @throws java.lang.IllegalArgumentException
* a strategy by the same name has already been registered.
*/
public static synchronized void register(final String name,
final MergeStrategy imp) {
if (STRATEGIES.containsKey(name))
throw new IllegalArgumentException(MessageFormat.format(
JGitText.get().mergeStrategyAlreadyExistsAsDefault, name));
STRATEGIES.put(name, imp);
}
/**
* Locate a strategy by name.
*
* @param name
* name of the strategy to locate.
* @return the strategy instance; null if no strategy matches the name.
*/
public static synchronized MergeStrategy get(String name) {
return STRATEGIES.get(name);
}
/**
* Get all registered strategies.
*
* @return the registered strategy instances. No inherit order is returned;
* the caller may modify (and/or sort) the returned array if
* necessary to obtain a reasonable ordering.
*/
public static synchronized MergeStrategy[] get() {
final MergeStrategy[] r = new MergeStrategy[STRATEGIES.size()];
STRATEGIES.values().toArray(r);
return r;
}
/**
* Get default name of this strategy implementation.
*
* @return default name of this strategy implementation.
*/
public abstract String getName();
/**
* Create a new merge instance.
*
* @param db
* repository database the merger will read from, and eventually
* write results back to.
* @return the new merge instance which implements this strategy.
*/
public abstract Merger newMerger(Repository db);
/**
* Create a new merge instance.
*
* @param db
* repository database the merger will read from, and eventually
* write results back to.
* @param inCore
* the merge will happen in memory, working folder will not be
* modified, in case of a non-trivial merge that requires manual
* resolution, the merger will fail.
* @return the new merge instance which implements this strategy.
*/
public abstract Merger newMerger(Repository db, boolean inCore);
/**
* Create a new merge instance.
* <p>
* The merge will happen in memory, working folder will not be modified, in
* case of a non-trivial merge that requires manual resolution, the merger
* will fail.
*
* @param inserter
* inserter to write results back to.
* @param config
* repo config for reading diff algorithm settings.
* @return the new merge instance which implements this strategy.
* @since 4.8
*/
public abstract Merger newMerger(ObjectInserter inserter, Config config);
}
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