RecursiveMerger.java
/*
* Copyright (C) 2012, Research In Motion Limited
* Copyright (C) 2012, Christian Halstrick <christian.halstrick@sap.com> 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
*/
/*
* Contributors:
* George Young - initial API and implementation
* Christian Halstrick - initial API and implementation
*/
package org.eclipse.jgit.merge;
import java.io.IOException;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.TimeZone;
import org.eclipse.jgit.dircache.DirCache;
import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.errors.NoMergeBaseException;
import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.lib.CommitBuilder;
import org.eclipse.jgit.lib.Config;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectInserter;
import org.eclipse.jgit.lib.PersonIdent;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.filter.RevFilter;
import org.eclipse.jgit.treewalk.AbstractTreeIterator;
import org.eclipse.jgit.treewalk.EmptyTreeIterator;
import org.eclipse.jgit.treewalk.WorkingTreeIterator;
/**
* A three-way merger performing a content-merge if necessary across multiple
* bases using recursion
*
* This merger extends the resolve merger and does several things differently:
*
* - allow more than one merge base, up to a maximum
*
* - uses "Lists" instead of Arrays for chained types
*
* - recursively merges the merge bases together to compute a usable base
*
* @since 3.0
*/
public class RecursiveMerger extends ResolveMerger {
/**
* The maximum number of merge bases. This merge will stop when the number
* of merge bases exceeds this value
*/
public final int MAX_BASES = 200;
/**
* Normal recursive merge when you want a choice of DirCache placement
* inCore
*
* @param local
* a {@link org.eclipse.jgit.lib.Repository} object.
* @param inCore
* a boolean.
*/
protected RecursiveMerger(Repository local, boolean inCore) {
super(local, inCore);
}
/**
* Normal recursive merge, implies not inCore
*
* @param local a {@link org.eclipse.jgit.lib.Repository} object.
*/
protected RecursiveMerger(Repository local) {
this(local, false);
}
/**
* Normal recursive merge, implies inCore.
*
* @param inserter
* an {@link org.eclipse.jgit.lib.ObjectInserter} object.
* @param config
* the repository configuration
* @since 4.8
*/
protected RecursiveMerger(ObjectInserter inserter, Config config) {
super(inserter, config);
}
/**
* {@inheritDoc}
* <p>
* Get a single base commit for two given commits. If the two source commits
* have more than one base commit recursively merge the base commits
* together until you end up with a single base commit.
*/
@Override
protected RevCommit getBaseCommit(RevCommit a, RevCommit b)
throws IncorrectObjectTypeException, IOException {
return getBaseCommit(a, b, 0);
}
/**
* Get a single base commit for two given commits. If the two source commits
* have more than one base commit recursively merge the base commits
* together until a virtual common base commit has been found.
*
* @param a
* the first commit to be merged
* @param b
* the second commit to be merged
* @param callDepth
* the callDepth when this method is called recursively
* @return the merge base of two commits. If a criss-cross merge required a
* synthetic merge base this commit is visible only the merger's
* RevWalk and will not be in the repository.
* @throws java.io.IOException
* @throws IncorrectObjectTypeException
* one of the input objects is not a commit.
* @throws NoMergeBaseException
* too many merge bases are found or the computation of a common
* merge base failed (e.g. because of a conflict).
*/
protected RevCommit getBaseCommit(RevCommit a, RevCommit b, int callDepth)
throws IOException {
ArrayList<RevCommit> baseCommits = new ArrayList<>();
walk.reset();
walk.setRevFilter(RevFilter.MERGE_BASE);
walk.markStart(a);
walk.markStart(b);
RevCommit c;
while ((c = walk.next()) != null)
baseCommits.add(c);
if (baseCommits.isEmpty())
return null;
if (baseCommits.size() == 1)
return baseCommits.get(0);
if (baseCommits.size() >= MAX_BASES)
throw new NoMergeBaseException(NoMergeBaseException.MergeBaseFailureReason.TOO_MANY_MERGE_BASES, MessageFormat.format(
JGitText.get().mergeRecursiveTooManyMergeBasesFor,
Integer.valueOf(MAX_BASES), a.name(), b.name(),
Integer.valueOf(baseCommits.size())));
// We know we have more than one base commit. We have to do merges now
// to determine a single base commit. We don't want to spoil the current
// dircache and working tree with the results of this intermediate
// merges. Therefore set the dircache to a new in-memory dircache and
// disable that we update the working-tree. We set this back to the
// original values once a single base commit is created.
RevCommit currentBase = baseCommits.get(0);
DirCache oldDircache = dircache;
boolean oldIncore = inCore;
WorkingTreeIterator oldWTreeIt = workingTreeIterator;
workingTreeIterator = null;
try {
dircache = DirCache.read(reader, currentBase.getTree());
inCore = true;
List<RevCommit> parents = new ArrayList<>();
parents.add(currentBase);
for (int commitIdx = 1; commitIdx < baseCommits.size(); commitIdx++) {
RevCommit nextBase = baseCommits.get(commitIdx);
if (commitIdx >= MAX_BASES)
throw new NoMergeBaseException(
NoMergeBaseException.MergeBaseFailureReason.TOO_MANY_MERGE_BASES,
MessageFormat.format(
JGitText.get().mergeRecursiveTooManyMergeBasesFor,
Integer.valueOf(MAX_BASES), a.name(), b.name(),
Integer.valueOf(baseCommits.size())));
parents.add(nextBase);
RevCommit bc = getBaseCommit(currentBase, nextBase,
callDepth + 1);
AbstractTreeIterator bcTree = (bc == null) ? new EmptyTreeIterator()
: openTree(bc.getTree());
if (mergeTrees(bcTree, currentBase.getTree(),
nextBase.getTree(), true))
currentBase = createCommitForTree(resultTree, parents);
else
throw new NoMergeBaseException(
NoMergeBaseException.MergeBaseFailureReason.CONFLICTS_DURING_MERGE_BASE_CALCULATION,
MessageFormat.format(
JGitText.get().mergeRecursiveConflictsWhenMergingCommonAncestors,
currentBase.getName(), nextBase.getName()));
}
} finally {
inCore = oldIncore;
dircache = oldDircache;
workingTreeIterator = oldWTreeIt;
toBeCheckedOut.clear();
toBeDeleted.clear();
modifiedFiles.clear();
unmergedPaths.clear();
mergeResults.clear();
failingPaths.clear();
}
return currentBase;
}
/**
* Create a new commit by explicitly specifying the content tree and the
* parents. The commit message is not set and author/committer are set to
* the current user.
*
* @param tree
* the tree this commit should capture
* @param parents
* the list of parent commits
* @return a new commit visible only within this merger's RevWalk.
* @throws IOException
*/
private RevCommit createCommitForTree(ObjectId tree, List<RevCommit> parents)
throws IOException {
CommitBuilder c = new CommitBuilder();
c.setTreeId(tree);
c.setParentIds(parents);
c.setAuthor(mockAuthor(parents));
c.setCommitter(c.getAuthor());
return RevCommit.parse(walk, c.build());
}
private static PersonIdent mockAuthor(List<RevCommit> parents) {
String name = RecursiveMerger.class.getSimpleName();
int time = 0;
for (RevCommit p : parents)
time = Math.max(time, p.getCommitTime());
return new PersonIdent(
name, name + "@JGit", //$NON-NLS-1$
new Date((time + 1) * 1000L),
TimeZone.getTimeZone("GMT+0000")); //$NON-NLS-1$
}
}