xref: /JGit/org.eclipse.jgit/src/org/eclipse/jgit/api/DescribeCommand.java (revision 276fcb2a11aafbec488ac57de7c01ab7932762d9)
1f045a68aSKohsuke Kawaguchi /*
25c5f7c6bSMatthias Sohn  * Copyright (C) 2013, CloudBees, Inc. and others
3f045a68aSKohsuke Kawaguchi  *
45c5f7c6bSMatthias Sohn  * This program and the accompanying materials are made available under the
55c5f7c6bSMatthias Sohn  * terms of the Eclipse Distribution License v. 1.0 which is available at
65c5f7c6bSMatthias Sohn  * https://www.eclipse.org/org/documents/edl-v10.php.
7f045a68aSKohsuke Kawaguchi  *
85c5f7c6bSMatthias Sohn  * SPDX-License-Identifier: BSD-3-Clause
9f045a68aSKohsuke Kawaguchi  */
10f045a68aSKohsuke Kawaguchi package org.eclipse.jgit.api;
11f045a68aSKohsuke Kawaguchi 
12*276fcb2aSJason Yeo import static org.eclipse.jgit.lib.Constants.R_REFS;
130cf902e4SShawn Pearce import static org.eclipse.jgit.lib.Constants.R_TAGS;
14f045a68aSKohsuke Kawaguchi 
15f045a68aSKohsuke Kawaguchi import java.io.IOException;
16f045a68aSKohsuke Kawaguchi import java.text.MessageFormat;
17f045a68aSKohsuke Kawaguchi import java.util.ArrayList;
18060f3699SOliver Lockwood import java.util.Collection;
19f045a68aSKohsuke Kawaguchi import java.util.Collections;
20f045a68aSKohsuke Kawaguchi import java.util.Comparator;
21f9de9175SHåvard Wall import java.util.Date;
22f045a68aSKohsuke Kawaguchi import java.util.List;
23f045a68aSKohsuke Kawaguchi import java.util.Map;
24060f3699SOliver Lockwood import java.util.Optional;
25060f3699SOliver Lockwood import java.util.stream.Collectors;
26df626364SMatthias Sohn import java.util.stream.Stream;
27f045a68aSKohsuke Kawaguchi 
280cf902e4SShawn Pearce import org.eclipse.jgit.api.errors.GitAPIException;
290cf902e4SShawn Pearce import org.eclipse.jgit.api.errors.JGitInternalException;
300cf902e4SShawn Pearce import org.eclipse.jgit.api.errors.RefNotFoundException;
310cf902e4SShawn Pearce import org.eclipse.jgit.errors.IncorrectObjectTypeException;
32af0867cbSOliver Lockwood import org.eclipse.jgit.errors.InvalidPatternException;
330cf902e4SShawn Pearce import org.eclipse.jgit.errors.MissingObjectException;
3410ab407fSThomas Wolf import org.eclipse.jgit.fnmatch.FileNameMatcher;
350cf902e4SShawn Pearce import org.eclipse.jgit.internal.JGitText;
360cf902e4SShawn Pearce import org.eclipse.jgit.lib.Constants;
370cf902e4SShawn Pearce import org.eclipse.jgit.lib.ObjectId;
380cf902e4SShawn Pearce import org.eclipse.jgit.lib.Ref;
390cf902e4SShawn Pearce import org.eclipse.jgit.lib.Repository;
400cf902e4SShawn Pearce import org.eclipse.jgit.revwalk.RevCommit;
410cf902e4SShawn Pearce import org.eclipse.jgit.revwalk.RevFlag;
420cf902e4SShawn Pearce import org.eclipse.jgit.revwalk.RevFlagSet;
43f9de9175SHåvard Wall import org.eclipse.jgit.revwalk.RevTag;
440cf902e4SShawn Pearce import org.eclipse.jgit.revwalk.RevWalk;
45f045a68aSKohsuke Kawaguchi 
46f045a68aSKohsuke Kawaguchi /**
47f045a68aSKohsuke Kawaguchi  * Given a commit, show the most recent tag that is reachable from a commit.
48f045a68aSKohsuke Kawaguchi  *
4972c76185SMatthias Sohn  * @since 3.2
50f045a68aSKohsuke Kawaguchi  */
51f045a68aSKohsuke Kawaguchi public class DescribeCommand extends GitCommand<String> {
52f045a68aSKohsuke Kawaguchi 	private final RevWalk w;
53f045a68aSKohsuke Kawaguchi 
54f045a68aSKohsuke Kawaguchi 	/**
55f045a68aSKohsuke Kawaguchi 	 * Commit to describe.
56f045a68aSKohsuke Kawaguchi 	 */
57f045a68aSKohsuke Kawaguchi 	private RevCommit target;
58f045a68aSKohsuke Kawaguchi 
59f045a68aSKohsuke Kawaguchi 	/**
60f045a68aSKohsuke Kawaguchi 	 * How many tags we'll consider as candidates.
61f045a68aSKohsuke Kawaguchi 	 * This can only go up to the number of flags JGit can support in a walk,
62f045a68aSKohsuke Kawaguchi 	 * which is 24.
63f045a68aSKohsuke Kawaguchi 	 */
64f045a68aSKohsuke Kawaguchi 	private int maxCandidates = 10;
65f045a68aSKohsuke Kawaguchi 
66f045a68aSKohsuke Kawaguchi 	/**
670e3ddea1SChristian Halstrick 	 * Whether to always use long output format or not.
680e3ddea1SChristian Halstrick 	 */
690e3ddea1SChristian Halstrick 	private boolean longDesc;
700e3ddea1SChristian Halstrick 
710e3ddea1SChristian Halstrick 	/**
72d9e16538SSebastian Schuberth 	 * Pattern matchers to be applied to tags under consideration.
73af0867cbSOliver Lockwood 	 */
7410ab407fSThomas Wolf 	private List<FileNameMatcher> matchers = new ArrayList<>();
75af0867cbSOliver Lockwood 
76af0867cbSOliver Lockwood 	/**
77*276fcb2aSJason Yeo 	 * Whether to use all refs in the refs/ namespace
78*276fcb2aSJason Yeo 	 */
79*276fcb2aSJason Yeo 	private boolean useAll;
80*276fcb2aSJason Yeo 
81*276fcb2aSJason Yeo 	/**
82d9e16538SSebastian Schuberth 	 * Whether to use all tags (incl. lightweight) or not.
835429d1a0SMarcel Trautwein 	 */
84afcb3a8cSSebastian Schuberth 	private boolean useTags;
855429d1a0SMarcel Trautwein 
865429d1a0SMarcel Trautwein 	/**
87237c76fdSSebastian Schuberth 	 * Whether to show a uniquely abbreviated commit hash as a fallback or not.
88237c76fdSSebastian Schuberth 	 */
89237c76fdSSebastian Schuberth 	private boolean always;
90237c76fdSSebastian Schuberth 
91237c76fdSSebastian Schuberth 	/**
920210e0e2SMatthias Sohn 	 * Constructor for DescribeCommand.
93f045a68aSKohsuke Kawaguchi 	 *
94f045a68aSKohsuke Kawaguchi 	 * @param repo
950210e0e2SMatthias Sohn 	 *            the {@link org.eclipse.jgit.lib.Repository}
96f045a68aSKohsuke Kawaguchi 	 */
DescribeCommand(Repository repo)97f045a68aSKohsuke Kawaguchi 	protected DescribeCommand(Repository repo) {
98f045a68aSKohsuke Kawaguchi 		super(repo);
99f045a68aSKohsuke Kawaguchi 		w = new RevWalk(repo);
100f045a68aSKohsuke Kawaguchi 		w.setRetainBody(false);
101f045a68aSKohsuke Kawaguchi 	}
102f045a68aSKohsuke Kawaguchi 
103f045a68aSKohsuke Kawaguchi 	/**
104f045a68aSKohsuke Kawaguchi 	 * Sets the commit to be described.
105f045a68aSKohsuke Kawaguchi 	 *
106f045a68aSKohsuke Kawaguchi 	 * @param target
107f045a68aSKohsuke Kawaguchi 	 * 		A non-null object ID to be described.
108f045a68aSKohsuke Kawaguchi 	 * @return {@code this}
109f045a68aSKohsuke Kawaguchi 	 * @throws MissingObjectException
110f045a68aSKohsuke Kawaguchi 	 *             the supplied commit does not exist.
111f045a68aSKohsuke Kawaguchi 	 * @throws IncorrectObjectTypeException
112f045a68aSKohsuke Kawaguchi 	 *             the supplied id is not a commit or an annotated tag.
1130210e0e2SMatthias Sohn 	 * @throws java.io.IOException
114f045a68aSKohsuke Kawaguchi 	 *             a pack file or loose object could not be read.
115f045a68aSKohsuke Kawaguchi 	 */
setTarget(ObjectId target)1163c2c8b47SMatthias Sohn 	public DescribeCommand setTarget(ObjectId target) throws IOException {
117f045a68aSKohsuke Kawaguchi 		this.target = w.parseCommit(target);
118f045a68aSKohsuke Kawaguchi 		return this;
119f045a68aSKohsuke Kawaguchi 	}
120f045a68aSKohsuke Kawaguchi 
121f045a68aSKohsuke Kawaguchi 	/**
122f045a68aSKohsuke Kawaguchi 	 * Sets the commit to be described.
123f045a68aSKohsuke Kawaguchi 	 *
124f045a68aSKohsuke Kawaguchi 	 * @param rev
1250210e0e2SMatthias Sohn 	 *            Commit ID, tag, branch, ref, etc. See
1260210e0e2SMatthias Sohn 	 *            {@link org.eclipse.jgit.lib.Repository#resolve(String)} for
1270210e0e2SMatthias Sohn 	 *            allowed syntax.
128f045a68aSKohsuke Kawaguchi 	 * @return {@code this}
129f045a68aSKohsuke Kawaguchi 	 * @throws IncorrectObjectTypeException
130f045a68aSKohsuke Kawaguchi 	 *             the supplied id is not a commit or an annotated tag.
1310210e0e2SMatthias Sohn 	 * @throws org.eclipse.jgit.api.errors.RefNotFoundException
132f045a68aSKohsuke Kawaguchi 	 *             the given rev didn't resolve to any object.
1330210e0e2SMatthias Sohn 	 * @throws java.io.IOException
134f045a68aSKohsuke Kawaguchi 	 *             a pack file or loose object could not be read.
135f045a68aSKohsuke Kawaguchi 	 */
setTarget(String rev)1363c2c8b47SMatthias Sohn 	public DescribeCommand setTarget(String rev) throws IOException,
1373c2c8b47SMatthias Sohn 			RefNotFoundException {
138f045a68aSKohsuke Kawaguchi 		ObjectId id = repo.resolve(rev);
139f045a68aSKohsuke Kawaguchi 		if (id == null)
140f045a68aSKohsuke Kawaguchi 			throw new RefNotFoundException(MessageFormat.format(JGitText.get().refNotResolved, rev));
141f045a68aSKohsuke Kawaguchi 		return setTarget(id);
142f045a68aSKohsuke Kawaguchi 	}
143f045a68aSKohsuke Kawaguchi 
144f045a68aSKohsuke Kawaguchi 	/**
1450e3ddea1SChristian Halstrick 	 * Determine whether always to use the long format or not. When set to
1460e3ddea1SChristian Halstrick 	 * <code>true</code> the long format is used even the commit matches a tag.
1470e3ddea1SChristian Halstrick 	 *
1480e3ddea1SChristian Halstrick 	 * @param longDesc
1490e3ddea1SChristian Halstrick 	 *            <code>true</code> if always the long format should be used.
1500e3ddea1SChristian Halstrick 	 * @return {@code this}
1510e3ddea1SChristian Halstrick 	 * @see <a
1520e3ddea1SChristian Halstrick 	 *      href="https://www.kernel.org/pub/software/scm/git/docs/git-describe.html"
1530e3ddea1SChristian Halstrick 	 *      >Git documentation about describe</a>
1540e3ddea1SChristian Halstrick 	 * @since 4.0
1550e3ddea1SChristian Halstrick 	 */
setLong(boolean longDesc)1560e3ddea1SChristian Halstrick 	public DescribeCommand setLong(boolean longDesc) {
1570e3ddea1SChristian Halstrick 		this.longDesc = longDesc;
1580e3ddea1SChristian Halstrick 		return this;
1590e3ddea1SChristian Halstrick 	}
1600e3ddea1SChristian Halstrick 
1615429d1a0SMarcel Trautwein 	/**
162*276fcb2aSJason Yeo 	 * Instead of using only the annotated tags, use any ref found in refs/
163*276fcb2aSJason Yeo 	 * namespace. This option enables matching any known branch,
164*276fcb2aSJason Yeo 	 * remote-tracking branch, or lightweight tag.
165*276fcb2aSJason Yeo 	 *
166*276fcb2aSJason Yeo 	 * @param all
167*276fcb2aSJason Yeo 	 *            <code>true</code> enables matching any ref found in refs/
168*276fcb2aSJason Yeo 	 *            like setting option --all in c git
169*276fcb2aSJason Yeo 	 * @return {@code this}
170*276fcb2aSJason Yeo 	 * @since 5.10
171*276fcb2aSJason Yeo 	 */
setAll(boolean all)172*276fcb2aSJason Yeo 	public DescribeCommand setAll(boolean all) {
173*276fcb2aSJason Yeo 		this.useAll = all;
174*276fcb2aSJason Yeo 		return this;
175*276fcb2aSJason Yeo 	}
176*276fcb2aSJason Yeo 
177*276fcb2aSJason Yeo 	/**
1785429d1a0SMarcel Trautwein 	 * Instead of using only the annotated tags, use any tag found in refs/tags
1795429d1a0SMarcel Trautwein 	 * namespace. This option enables matching lightweight (non-annotated) tags
1805429d1a0SMarcel Trautwein 	 * or not.
1815429d1a0SMarcel Trautwein 	 *
1825429d1a0SMarcel Trautwein 	 * @param tags
1835429d1a0SMarcel Trautwein 	 *            <code>true</code> enables matching lightweight (non-annotated)
1845429d1a0SMarcel Trautwein 	 *            tags like setting option --tags in c git
1855429d1a0SMarcel Trautwein 	 * @return {@code this}
1865429d1a0SMarcel Trautwein 	 * @since 5.0
1875429d1a0SMarcel Trautwein 	 */
setTags(boolean tags)1885429d1a0SMarcel Trautwein 	public DescribeCommand setTags(boolean tags) {
1895429d1a0SMarcel Trautwein 		this.useTags = tags;
1905429d1a0SMarcel Trautwein 		return this;
1915429d1a0SMarcel Trautwein 	}
1925429d1a0SMarcel Trautwein 
193237c76fdSSebastian Schuberth 	/**
194237c76fdSSebastian Schuberth 	 * Always describe the commit by eventually falling back to a uniquely
195237c76fdSSebastian Schuberth 	 * abbreviated commit hash if no other name matches.
196237c76fdSSebastian Schuberth 	 *
197237c76fdSSebastian Schuberth 	 * @param always
198237c76fdSSebastian Schuberth 	 *            <code>true</code> enables falling back to a uniquely
199237c76fdSSebastian Schuberth 	 *            abbreviated commit hash
200237c76fdSSebastian Schuberth 	 * @return {@code this}
201237c76fdSSebastian Schuberth 	 * @since 5.4
202237c76fdSSebastian Schuberth 	 */
setAlways(boolean always)203237c76fdSSebastian Schuberth 	public DescribeCommand setAlways(boolean always) {
204237c76fdSSebastian Schuberth 		this.always = always;
205237c76fdSSebastian Schuberth 		return this;
206237c76fdSSebastian Schuberth 	}
207237c76fdSSebastian Schuberth 
longDescription(Ref tag, int depth, ObjectId tip)2080e3ddea1SChristian Halstrick 	private String longDescription(Ref tag, int depth, ObjectId tip)
2090e3ddea1SChristian Halstrick 			throws IOException {
2100e3ddea1SChristian Halstrick 		return String.format(
211*276fcb2aSJason Yeo 				"%s-%d-g%s", formatRefName(tag.getName()), //$NON-NLS-1$
2120e3ddea1SChristian Halstrick 				Integer.valueOf(depth), w.getObjectReader().abbreviate(tip)
2130e3ddea1SChristian Halstrick 						.name());
2140e3ddea1SChristian Halstrick 	}
2150e3ddea1SChristian Halstrick 
2160e3ddea1SChristian Halstrick 	/**
2170210e0e2SMatthias Sohn 	 * Sets one or more {@code glob(7)} patterns that tags must match to be
2180210e0e2SMatthias Sohn 	 * considered. If multiple patterns are provided, tags only need match one
2190210e0e2SMatthias Sohn 	 * of them.
220af0867cbSOliver Lockwood 	 *
2210210e0e2SMatthias Sohn 	 * @param patterns
2220210e0e2SMatthias Sohn 	 *            the {@code glob(7)} pattern or patterns
223af0867cbSOliver Lockwood 	 * @return {@code this}
2240210e0e2SMatthias Sohn 	 * @throws org.eclipse.jgit.errors.InvalidPatternException
2250210e0e2SMatthias Sohn 	 *             if the pattern passed in was invalid.
2260210e0e2SMatthias Sohn 	 * @see <a href=
2270210e0e2SMatthias Sohn 	 *      "https://www.kernel.org/pub/software/scm/git/docs/git-describe.html"
228af0867cbSOliver Lockwood 	 *      >Git documentation about describe</a>
229af0867cbSOliver Lockwood 	 * @since 4.9
230af0867cbSOliver Lockwood 	 */
setMatch(String... patterns)231af0867cbSOliver Lockwood 	public DescribeCommand setMatch(String... patterns) throws InvalidPatternException {
232af0867cbSOliver Lockwood 		for (String p : patterns) {
23310ab407fSThomas Wolf 			matchers.add(new FileNameMatcher(p, null));
234af0867cbSOliver Lockwood 		}
235af0867cbSOliver Lockwood 		return this;
236af0867cbSOliver Lockwood 	}
237af0867cbSOliver Lockwood 
238f9de9175SHåvard Wall 	private final Comparator<Ref> TAG_TIE_BREAKER = new Comparator<Ref>() {
239f9de9175SHåvard Wall 
240f9de9175SHåvard Wall 		@Override
241f9de9175SHåvard Wall 		public int compare(Ref o1, Ref o2) {
242f9de9175SHåvard Wall 			try {
243f9de9175SHåvard Wall 				return tagDate(o2).compareTo(tagDate(o1));
244f9de9175SHåvard Wall 			} catch (IOException e) {
245f9de9175SHåvard Wall 				return 0;
246f9de9175SHåvard Wall 			}
247f9de9175SHåvard Wall 		}
248f9de9175SHåvard Wall 
249f9de9175SHåvard Wall 		private Date tagDate(Ref tag) throws IOException {
250f9de9175SHåvard Wall 			RevTag t = w.parseTag(tag.getObjectId());
251f9de9175SHåvard Wall 			w.parseBody(t);
252f9de9175SHåvard Wall 			return t.getTaggerIdent().getWhen();
253f9de9175SHåvard Wall 		}
254f9de9175SHåvard Wall 	};
255f9de9175SHåvard Wall 
getBestMatch(List<Ref> tags)256060f3699SOliver Lockwood 	private Optional<Ref> getBestMatch(List<Ref> tags) {
2576a4c77e6SCarsten Hammer 		if (tags == null || tags.isEmpty()) {
258060f3699SOliver Lockwood 			return Optional.empty();
2596a4c77e6SCarsten Hammer 		} else if (matchers.isEmpty()) {
260f9de9175SHåvard Wall 			Collections.sort(tags, TAG_TIE_BREAKER);
261060f3699SOliver Lockwood 			return Optional.of(tags.get(0));
262af0867cbSOliver Lockwood 		} else {
263df626364SMatthias Sohn 			// Find the first tag that matches in the stream of all tags
264df626364SMatthias Sohn 			// filtered by matchers ordered by tie break order
265df626364SMatthias Sohn 			Stream<Ref> matchingTags = Stream.empty();
26610ab407fSThomas Wolf 			for (FileNameMatcher matcher : matchers) {
267df626364SMatthias Sohn 				Stream<Ref> m = tags.stream().filter(
26810ab407fSThomas Wolf 						tag -> {
269*276fcb2aSJason Yeo 							matcher.append(formatRefName(tag.getName()));
27010ab407fSThomas Wolf 							boolean result = matcher.isMatch();
27110ab407fSThomas Wolf 							matcher.reset();
27210ab407fSThomas Wolf 							return result;
27310ab407fSThomas Wolf 						});
274df626364SMatthias Sohn 				matchingTags = Stream.of(matchingTags, m).flatMap(i -> i);
275af0867cbSOliver Lockwood 			}
276df626364SMatthias Sohn 			return matchingTags.sorted(TAG_TIE_BREAKER).findFirst();
277060f3699SOliver Lockwood 		}
278060f3699SOliver Lockwood 	}
279060f3699SOliver Lockwood 
getObjectIdFromRef(Ref r)28051599ebbSDavid Pursehouse 	private ObjectId getObjectIdFromRef(Ref r) throws JGitInternalException {
28151599ebbSDavid Pursehouse 		try {
28251599ebbSDavid Pursehouse 			ObjectId key = repo.getRefDatabase().peel(r).getPeeledObjectId();
283060f3699SOliver Lockwood 			if (key == null) {
284060f3699SOliver Lockwood 				key = r.getObjectId();
285060f3699SOliver Lockwood 			}
286060f3699SOliver Lockwood 			return key;
28751599ebbSDavid Pursehouse 		} catch (IOException e) {
28851599ebbSDavid Pursehouse 			throw new JGitInternalException(e.getMessage(), e);
28951599ebbSDavid Pursehouse 		}
290060f3699SOliver Lockwood 	}
291af0867cbSOliver Lockwood 
292af0867cbSOliver Lockwood 	/**
2930210e0e2SMatthias Sohn 	 * {@inheritDoc}
2940210e0e2SMatthias Sohn 	 * <p>
295b15c617dSMatthias Sohn 	 * Describes the specified commit. Target defaults to HEAD if no commit was
296b15c617dSMatthias Sohn 	 * set explicitly.
297f045a68aSKohsuke Kawaguchi 	 */
298f045a68aSKohsuke Kawaguchi 	@Override
call()299f045a68aSKohsuke Kawaguchi 	public String call() throws GitAPIException {
300f045a68aSKohsuke Kawaguchi 		try {
301f045a68aSKohsuke Kawaguchi 			checkCallable();
3025429d1a0SMarcel Trautwein 			if (target == null) {
303b15c617dSMatthias Sohn 				setTarget(Constants.HEAD);
3045429d1a0SMarcel Trautwein 			}
305f045a68aSKohsuke Kawaguchi 
3069edf9bf2SMatthias Sohn 			Collection<Ref> tagList = repo.getRefDatabase()
307*276fcb2aSJason Yeo 					.getRefsByPrefix(useAll ? R_REFS : R_TAGS);
308060f3699SOliver Lockwood 			Map<ObjectId, List<Ref>> tags = tagList.stream()
3095429d1a0SMarcel Trautwein 					.filter(this::filterLightweightTags)
310060f3699SOliver Lockwood 					.collect(Collectors.groupingBy(this::getObjectIdFromRef));
311f045a68aSKohsuke Kawaguchi 
312f045a68aSKohsuke Kawaguchi 			// combined flags of all the candidate instances
313f045a68aSKohsuke Kawaguchi 			final RevFlagSet allFlags = new RevFlagSet();
314f045a68aSKohsuke Kawaguchi 
315f045a68aSKohsuke Kawaguchi 			/**
316f045a68aSKohsuke Kawaguchi 			 * Tracks the depth of each tag as we find them.
317f045a68aSKohsuke Kawaguchi 			 */
318f045a68aSKohsuke Kawaguchi 			class Candidate {
319f045a68aSKohsuke Kawaguchi 				final Ref tag;
320f045a68aSKohsuke Kawaguchi 				final RevFlag flag;
321f045a68aSKohsuke Kawaguchi 
322f045a68aSKohsuke Kawaguchi 				/**
323f045a68aSKohsuke Kawaguchi 				 * This field counts number of commits that are reachable from
324f045a68aSKohsuke Kawaguchi 				 * the tip but not reachable from the tag.
325f045a68aSKohsuke Kawaguchi 				 */
326f045a68aSKohsuke Kawaguchi 				int depth;
327f045a68aSKohsuke Kawaguchi 
328f045a68aSKohsuke Kawaguchi 				Candidate(RevCommit commit, Ref tag) {
329f045a68aSKohsuke Kawaguchi 					this.tag = tag;
330f045a68aSKohsuke Kawaguchi 					this.flag = w.newFlag(tag.getName());
331f045a68aSKohsuke Kawaguchi 					// we'll mark all the nodes reachable from this tag accordingly
332f045a68aSKohsuke Kawaguchi 					allFlags.add(flag);
333f045a68aSKohsuke Kawaguchi 					w.carry(flag);
334f045a68aSKohsuke Kawaguchi 					commit.add(flag);
335f045a68aSKohsuke Kawaguchi 					// As of this writing, JGit carries a flag from a child to its parents
336f045a68aSKohsuke Kawaguchi 					// right before RevWalk.next() returns, so all the flags that are added
337f045a68aSKohsuke Kawaguchi 					// must be manually carried to its parents. If that gets fixed,
338f045a68aSKohsuke Kawaguchi 					// this will be unnecessary.
339f045a68aSKohsuke Kawaguchi 					commit.carry(flag);
340f045a68aSKohsuke Kawaguchi 				}
341f045a68aSKohsuke Kawaguchi 
342f045a68aSKohsuke Kawaguchi 				/**
343f045a68aSKohsuke Kawaguchi 				 * Does this tag contain the given commit?
344f045a68aSKohsuke Kawaguchi 				 */
345f045a68aSKohsuke Kawaguchi 				boolean reaches(RevCommit c) {
346f045a68aSKohsuke Kawaguchi 					return c.has(flag);
347f045a68aSKohsuke Kawaguchi 				}
348f045a68aSKohsuke Kawaguchi 
349f045a68aSKohsuke Kawaguchi 				String describe(ObjectId tip) throws IOException {
3500e3ddea1SChristian Halstrick 					return longDescription(tag, depth, tip);
351f045a68aSKohsuke Kawaguchi 				}
3520e3ddea1SChristian Halstrick 
353f045a68aSKohsuke Kawaguchi 			}
3543b444863SDavid Pursehouse 			List<Candidate> candidates = new ArrayList<>();    // all the candidates we find
355f045a68aSKohsuke Kawaguchi 
356060f3699SOliver Lockwood 			// is the target already pointing to a suitable tag? if so, we are done!
357060f3699SOliver Lockwood 			Optional<Ref> bestMatch = getBestMatch(tags.get(target));
358060f3699SOliver Lockwood 			if (bestMatch.isPresent()) {
359060f3699SOliver Lockwood 				return longDesc ? longDescription(bestMatch.get(), 0, target) :
360*276fcb2aSJason Yeo 						formatRefName(bestMatch.get().getName());
3610e3ddea1SChristian Halstrick 			}
362f045a68aSKohsuke Kawaguchi 
363f045a68aSKohsuke Kawaguchi 			w.markStart(target);
364f045a68aSKohsuke Kawaguchi 
365f045a68aSKohsuke Kawaguchi 			int seen = 0;   // commit seen thus far
366f045a68aSKohsuke Kawaguchi 			RevCommit c;
367f045a68aSKohsuke Kawaguchi 			while ((c = w.next()) != null) {
368f045a68aSKohsuke Kawaguchi 				if (!c.hasAny(allFlags)) {
369f045a68aSKohsuke Kawaguchi 					// if a tag already dominates this commit,
370f045a68aSKohsuke Kawaguchi 					// then there's no point in picking a tag on this commit
371f045a68aSKohsuke Kawaguchi 					// since the one that dominates it is always more preferable
372060f3699SOliver Lockwood 					bestMatch = getBestMatch(tags.get(c));
373060f3699SOliver Lockwood 					if (bestMatch.isPresent()) {
374060f3699SOliver Lockwood 						Candidate cd = new Candidate(c, bestMatch.get());
375f045a68aSKohsuke Kawaguchi 						candidates.add(cd);
376f045a68aSKohsuke Kawaguchi 						cd.depth = seen;
377f045a68aSKohsuke Kawaguchi 					}
378f045a68aSKohsuke Kawaguchi 				}
379f045a68aSKohsuke Kawaguchi 
380f045a68aSKohsuke Kawaguchi 				// if the newly discovered commit isn't reachable from a tag that we've seen
381f045a68aSKohsuke Kawaguchi 				// it counts toward the total depth.
382f045a68aSKohsuke Kawaguchi 				for (Candidate cd : candidates) {
383f045a68aSKohsuke Kawaguchi 					if (!cd.reaches(c))
384f045a68aSKohsuke Kawaguchi 						cd.depth++;
385f045a68aSKohsuke Kawaguchi 				}
386f045a68aSKohsuke Kawaguchi 
387f045a68aSKohsuke Kawaguchi 				// if we have search going for enough tags, we will start
388f045a68aSKohsuke Kawaguchi 				// closing down. JGit can only give us a finite number of bits,
389f045a68aSKohsuke Kawaguchi 				// so we can't track all tags even if we wanted to.
390f045a68aSKohsuke Kawaguchi 				if (candidates.size() >= maxCandidates)
391f045a68aSKohsuke Kawaguchi 					break;
392f045a68aSKohsuke Kawaguchi 
393f045a68aSKohsuke Kawaguchi 				// TODO: if all the commits in the queue of RevWalk has allFlags
394f045a68aSKohsuke Kawaguchi 				// there's no point in continuing search as we'll not discover any more
395f045a68aSKohsuke Kawaguchi 				// tags. But RevWalk doesn't expose this.
396f045a68aSKohsuke Kawaguchi 				seen++;
397f045a68aSKohsuke Kawaguchi 			}
398f045a68aSKohsuke Kawaguchi 
399f045a68aSKohsuke Kawaguchi 			// at this point we aren't adding any more tags to our search,
400f045a68aSKohsuke Kawaguchi 			// but we still need to count all the depths correctly.
401f045a68aSKohsuke Kawaguchi 			while ((c = w.next()) != null) {
402f045a68aSKohsuke Kawaguchi 				if (c.hasAll(allFlags)) {
403f045a68aSKohsuke Kawaguchi 					// no point in visiting further from here, so cut the search here
404f045a68aSKohsuke Kawaguchi 					for (RevCommit p : c.getParents())
405f045a68aSKohsuke Kawaguchi 						p.add(RevFlag.SEEN);
406f045a68aSKohsuke Kawaguchi 				} else {
407f045a68aSKohsuke Kawaguchi 					for (Candidate cd : candidates) {
408f045a68aSKohsuke Kawaguchi 						if (!cd.reaches(c))
409f045a68aSKohsuke Kawaguchi 							cd.depth++;
410f045a68aSKohsuke Kawaguchi 					}
411f045a68aSKohsuke Kawaguchi 				}
412f045a68aSKohsuke Kawaguchi 			}
413f045a68aSKohsuke Kawaguchi 
414f045a68aSKohsuke Kawaguchi 			// if all the nodes are dominated by all the tags, the walk stops
415237c76fdSSebastian Schuberth 			if (candidates.isEmpty()) {
416237c76fdSSebastian Schuberth 				return always ? w.getObjectReader().abbreviate(target).name() : null;
417237c76fdSSebastian Schuberth 			}
418f045a68aSKohsuke Kawaguchi 
41984fc5c90SCarsten Hammer 			Candidate best = Collections.min(candidates,
42084fc5c90SCarsten Hammer 					(Candidate o1, Candidate o2) -> o1.depth - o2.depth);
421f045a68aSKohsuke Kawaguchi 
422f045a68aSKohsuke Kawaguchi 			return best.describe(target);
423f045a68aSKohsuke Kawaguchi 		} catch (IOException e) {
424f045a68aSKohsuke Kawaguchi 			throw new JGitInternalException(e.getMessage(), e);
425f045a68aSKohsuke Kawaguchi 		} finally {
426f045a68aSKohsuke Kawaguchi 			setCallable(false);
4275f8308bdSMatthias Sohn 			w.close();
428f045a68aSKohsuke Kawaguchi 		}
429f045a68aSKohsuke Kawaguchi 	}
4305429d1a0SMarcel Trautwein 
4315429d1a0SMarcel Trautwein 	/**
432*276fcb2aSJason Yeo 	 * Removes the refs/ or refs/tags prefix from tag names
433*276fcb2aSJason Yeo 	 * @param name the name of the tag
434*276fcb2aSJason Yeo 	 * @return the tag name with its prefix removed
435*276fcb2aSJason Yeo 	 */
formatRefName(String name)436*276fcb2aSJason Yeo 	private String formatRefName(String name) {
437*276fcb2aSJason Yeo 		return name.startsWith(R_TAGS) ? name.substring(R_TAGS.length()) :
438*276fcb2aSJason Yeo 				name.substring(R_REFS.length());
439*276fcb2aSJason Yeo 	}
440*276fcb2aSJason Yeo 
441*276fcb2aSJason Yeo 	/**
4425429d1a0SMarcel Trautwein 	 * Whether we use lightweight tags or not for describe Candidates
4435429d1a0SMarcel Trautwein 	 *
4445429d1a0SMarcel Trautwein 	 * @param ref
4455429d1a0SMarcel Trautwein 	 *            reference under inspection
4465429d1a0SMarcel Trautwein 	 * @return true if it should be used for describe or not regarding
4475429d1a0SMarcel Trautwein 	 *         {@link org.eclipse.jgit.api.DescribeCommand#useTags}
4485429d1a0SMarcel Trautwein 	 */
4495429d1a0SMarcel Trautwein 	@SuppressWarnings("null")
filterLightweightTags(Ref ref)4505429d1a0SMarcel Trautwein 	private boolean filterLightweightTags(Ref ref) {
4515429d1a0SMarcel Trautwein 		ObjectId id = ref.getObjectId();
4525429d1a0SMarcel Trautwein 		try {
453*276fcb2aSJason Yeo 			return this.useAll || this.useTags || (id != null && (w.parseTag(id) != null));
4545429d1a0SMarcel Trautwein 		} catch (IOException e) {
4555429d1a0SMarcel Trautwein 			return false;
4565429d1a0SMarcel Trautwein 		}
4575429d1a0SMarcel Trautwein 	}
458f045a68aSKohsuke Kawaguchi }
459