org.eclipse.jgit.api.DescribeCommand Maven / Gradle / Ivy
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package org.eclipse.jgit.api;
import org.eclipse.jgit.api.errors.GitAPIException;
import org.eclipse.jgit.api.errors.JGitInternalException;
import org.eclipse.jgit.api.errors.RefNotFoundException;
import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.errors.MissingObjectException;
import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.*;
import java.io.IOException;
import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import static org.eclipse.jgit.lib.Constants.R_TAGS;
/**
* Given a commit, show the most recent tag that is reachable from a commit.
*
* @since 3.2
*/
public class DescribeCommand extends GitCommand {
private final RevWalk w;
/**
* Commit to describe.
*/
private RevCommit target;
/**
* How many tags we'll consider as candidates.
* This can only go up to the number of flags JGit can support in a walk,
* which is 24.
*/
private int maxCandidates = 10;
/**
*
* @param repo
*/
protected DescribeCommand(Repository repo) {
super(repo);
w = new RevWalk(repo);
w.setRetainBody(false);
}
/**
* Sets the commit to be described.
*
* @param target
* A non-null object ID to be described.
* @return {@code this}
* @throws MissingObjectException
* the supplied commit does not exist.
* @throws IncorrectObjectTypeException
* the supplied id is not a commit or an annotated tag.
* @throws IOException
* a pack file or loose object could not be read.
*/
public DescribeCommand setTarget(ObjectId target) throws IOException {
this.target = w.parseCommit(target);
return this;
}
/**
* Sets the commit to be described.
*
* @param rev
* Commit ID, tag, branch, ref, etc.
* See {@link Repository#resolve(String)} for allowed syntax.
* @return {@code this}
* @throws IncorrectObjectTypeException
* the supplied id is not a commit or an annotated tag.
* @throws RefNotFoundException
* the given rev didn't resolve to any object.
* @throws IOException
* a pack file or loose object could not be read.
*/
public DescribeCommand setTarget(String rev) throws IOException,
RefNotFoundException {
ObjectId id = repo.resolve(rev);
if (id == null)
throw new RefNotFoundException(MessageFormat.format(JGitText.get().refNotResolved, rev));
return setTarget(id);
}
/**
* Describes the specified commit. Target defaults to HEAD if no commit was
* set explicitly.
*
* @return if there's a tag that points to the commit being described, this
* tag name is returned. Otherwise additional suffix is added to the
* nearest tag, just like git-describe(1).
*
* If none of the ancestors of the commit being described has any
* tags at all, then this method returns null, indicating that
* there's no way to describe this tag.
*/
@Override
public String call() throws GitAPIException {
try {
checkCallable();
if (target == null)
setTarget(Constants.HEAD);
Map tags = new HashMap();
for (Ref r : repo.getRefDatabase().getRefs(R_TAGS).values()) {
ObjectId key = repo.peel(r).getPeeledObjectId();
if (key == null)
key = r.getObjectId();
tags.put(key, r);
}
// combined flags of all the candidate instances
final RevFlagSet allFlags = new RevFlagSet();
/**
* Tracks the depth of each tag as we find them.
*/
class Candidate {
final Ref tag;
final RevFlag flag;
/**
* This field counts number of commits that are reachable from
* the tip but not reachable from the tag.
*/
int depth;
Candidate(RevCommit commit, Ref tag) {
this.tag = tag;
this.flag = w.newFlag(tag.getName());
// we'll mark all the nodes reachable from this tag accordingly
allFlags.add(flag);
w.carry(flag);
commit.add(flag);
// As of this writing, JGit carries a flag from a child to its parents
// right before RevWalk.next() returns, so all the flags that are added
// must be manually carried to its parents. If that gets fixed,
// this will be unnecessary.
commit.carry(flag);
}
/**
* Does this tag contain the given commit?
*/
boolean reaches(RevCommit c) {
return c.has(flag);
}
String describe(ObjectId tip) throws IOException {
return String.format("%s-%d-g%s", tag.getName().substring(R_TAGS.length()), //$NON-NLS-1$
Integer.valueOf(depth), w.getObjectReader().abbreviate(tip).name());
}
}
List candidates = new ArrayList(); // all the candidates we find
// is the target already pointing to a tag? if so, we are done!
Ref lucky = tags.get(target);
if (lucky != null)
return lucky.getName().substring(R_TAGS.length());
w.markStart(target);
int seen = 0; // commit seen thus far
RevCommit c;
while ((c = w.next()) != null) {
if (!c.hasAny(allFlags)) {
// if a tag already dominates this commit,
// then there's no point in picking a tag on this commit
// since the one that dominates it is always more preferable
Ref t = tags.get(c);
if (t != null) {
Candidate cd = new Candidate(c, t);
candidates.add(cd);
cd.depth = seen;
}
}
// if the newly discovered commit isn't reachable from a tag that we've seen
// it counts toward the total depth.
for (Candidate cd : candidates) {
if (!cd.reaches(c))
cd.depth++;
}
// if we have search going for enough tags, we will start
// closing down. JGit can only give us a finite number of bits,
// so we can't track all tags even if we wanted to.
if (candidates.size() >= maxCandidates)
break;
// TODO: if all the commits in the queue of RevWalk has allFlags
// there's no point in continuing search as we'll not discover any more
// tags. But RevWalk doesn't expose this.
seen++;
}
// at this point we aren't adding any more tags to our search,
// but we still need to count all the depths correctly.
while ((c = w.next()) != null) {
if (c.hasAll(allFlags)) {
// no point in visiting further from here, so cut the search here
for (RevCommit p : c.getParents())
p.add(RevFlag.SEEN);
} else {
for (Candidate cd : candidates) {
if (!cd.reaches(c))
cd.depth++;
}
}
}
// if all the nodes are dominated by all the tags, the walk stops
if (candidates.isEmpty())
return null;
Candidate best = Collections.min(candidates, new Comparator() {
public int compare(Candidate o1, Candidate o2) {
return o1.depth - o2.depth;
}
});
return best.describe(target);
} catch (IOException e) {
throw new JGitInternalException(e.getMessage(), e);
} finally {
setCallable(false);
w.release();
}
}
}