/*
* Copyright (C) 2008, Google Inc.
*
* 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 Git Development Community 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
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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package org.spearce.jgit.merge;
import java.io.IOException;
import org.spearce.jgit.errors.IncorrectObjectTypeException;
import org.spearce.jgit.lib.AnyObjectId;
import org.spearce.jgit.lib.Constants;
import org.spearce.jgit.lib.ObjectId;
import org.spearce.jgit.lib.ObjectWriter;
import org.spearce.jgit.lib.Repository;
import org.spearce.jgit.lib.WindowCursor;
import org.spearce.jgit.revwalk.RevCommit;
import org.spearce.jgit.revwalk.RevObject;
import org.spearce.jgit.revwalk.RevTree;
import org.spearce.jgit.revwalk.RevWalk;
import org.spearce.jgit.revwalk.filter.RevFilter;
import org.spearce.jgit.treewalk.AbstractTreeIterator;
import org.spearce.jgit.treewalk.CanonicalTreeParser;
import org.spearce.jgit.treewalk.EmptyTreeIterator;
/**
* Instance of a specific {@link MergeStrategy} for a single {@link Repository}.
*/
public abstract class Merger {
/** The repository this merger operates on. */
protected final Repository db;
/** A RevWalk for computing merge bases, or listing incoming commits. */
protected final RevWalk walk;
private ObjectWriter writer;
/** The original objects supplied in the merge; this can be any tree-ish. */
protected RevObject[] sourceObjects;
/** If {@link #sourceObjects}[i] is a commit, this is the commit. */
protected RevCommit[] sourceCommits;
/** The trees matching every entry in {@link #sourceObjects}. */
protected RevTree[] sourceTrees;
/**
* Create a new merge instance for a repository.
*
* @param local
* the repository this merger will read and write data on.
*/
protected Merger(final Repository local) {
db = local;
walk = new RevWalk(db);
}
/**
* @return the repository this merger operates on.
*/
public Repository getRepository() {
return db;
}
/**
* @return an object writer to create objects in {@link #getRepository()}.
*/
public ObjectWriter getObjectWriter() {
if (writer == null)
writer = new ObjectWriter(getRepository());
return writer;
}
/**
* Merge together two or more tree-ish objects.
* <p>
* Any tree-ish may be supplied as inputs. Commits and/or tags pointing at
* trees or commits may be passed as input objects.
*
* @param tips
* source trees to be combined together. The merge base is not
* included in this set.
* @return true if the merge was completed without conflicts; false if the
* merge strategy cannot handle this merge or there were conflicts
* preventing it from automatically resolving all paths.
* @throws IncorrectObjectTypeException
* one of the input objects is not a commit, but the strategy
* requires it to be a commit.
* @throws IOException
* one or more sources could not be read, or outputs could not
* be written to the Repository.
*/
public boolean merge(final AnyObjectId[] tips) throws IOException {
sourceObjects = new RevObject[tips.length];
for (int i = 0; i < tips.length; i++)
sourceObjects[i] = walk.parseAny(tips[i]);
sourceCommits = new RevCommit[sourceObjects.length];
for (int i = 0; i < sourceObjects.length; i++) {
try {
sourceCommits[i] = walk.parseCommit(sourceObjects[i]);
} catch (IncorrectObjectTypeException err) {
sourceCommits[i] = null;
}
}
sourceTrees = new RevTree[sourceObjects.length];
for (int i = 0; i < sourceObjects.length; i++)
sourceTrees[i] = walk.parseTree(sourceObjects[i]);
return mergeImpl();
}
/**
* Create an iterator to walk the merge base of two commits.
*
* @param aIdx
* index of the first commit in {@link #sourceObjects}.
* @param bIdx
* index of the second commit in {@link #sourceObjects}.
* @return the new iterator
* @throws IncorrectObjectTypeException
* one of the input objects is not a commit.
* @throws IOException
* objects are missing or multiple merge bases were found.
*/
protected AbstractTreeIterator mergeBase(final int aIdx, final int bIdx)
throws IOException {
if (sourceCommits[aIdx] == null)
throw new IncorrectObjectTypeException(sourceObjects[aIdx],
Constants.TYPE_COMMIT);
if (sourceCommits[bIdx] == null)
throw new IncorrectObjectTypeException(sourceObjects[bIdx],
Constants.TYPE_COMMIT);
walk.reset();
walk.setRevFilter(RevFilter.MERGE_BASE);
walk.markStart(sourceCommits[aIdx]);
walk.markStart(sourceCommits[bIdx]);
final RevCommit base = walk.next();
if (base == null)
return new EmptyTreeIterator();
final RevCommit base2 = walk.next();
if (base2 != null) {
throw new IOException("Multiple merge bases for:" + "\n "
+ sourceCommits[aIdx].name() + "\n "
+ sourceCommits[bIdx].name() + "found:" + "\n "
+ base.name() + "\n " + base2.name());
}
return openTree(base.getTree());
}
/**
* Open an iterator over a tree.
*
* @param treeId
* the tree to scan; must be a tree (not a treeish).
* @return an iterator for the tree.
* @throws IncorrectObjectTypeException
* the input object is not a tree.
* @throws IOException
* the tree object is not found or cannot be read.
*/
protected AbstractTreeIterator openTree(final AnyObjectId treeId)
throws IncorrectObjectTypeException, IOException {
final WindowCursor curs = new WindowCursor();
try {
return new CanonicalTreeParser(null, db, treeId, curs);
} finally {
curs.release();
}
}
/**
* Execute the merge.
* <p>
* This method is called from {@link #merge(AnyObjectId[])} after the
* {@link #sourceObjects}, {@link #sourceCommits} and {@link #sourceTrees}
* have been populated.
*
* @return true if the merge was completed without conflicts; false if the
* merge strategy cannot handle this merge or there were conflicts
* preventing it from automatically resolving all paths.
* @throws IncorrectObjectTypeException
* one of the input objects is not a commit, but the strategy
* requires it to be a commit.
* @throws IOException
* one or more sources could not be read, or outputs could not
* be written to the Repository.
*/
protected abstract boolean mergeImpl() throws IOException;
/**
* @return resulting tree, if {@link #merge(AnyObjectId[])} returned true.
*/
public abstract ObjectId getResultTreeId();
}