Get the latest commit in a repository with JGit

Question

I want to get the last commit metadata (the youngest one by date) in a repository using JGit.

I know that I can get the commit metadata using:

try (RevWalk walk = new RevWalk(repository))
{
    RevCommit commit = walk.parseCommit(repository.resolve(commitHash));
}

But how to get the latest commit hash?

Is there any other way to get the youngest by date RevCommit in a repository directly?

Can you clarify what _latest_ means exactly? Do you mean the youngest by date? From all branches? — Rüdiger Herrmann, Mar 15 '17 at 20:54
Yes Exactly, the yougest by date from all the branches. is it Important to look up for him for all the branches, because I thought that I can look up for him relatively to a repo regardless of the branches? — Master Mind, Mar 15 '17 at 20:59

score 10 · Answer 1 · edited Feb 28 '22 at 20:03

10

You could make use of git log and set it to only return the top most commit:

RevCommit latestCommit = new Git(repository).
   log().
   setMaxCount(1).
   call().
   iterator().
   next();

String latestCommitHash = latestCommit.getName();

edited Feb 28 '22 at 20:03

Nathan

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answered Dec 10 '19 at 19:46

jet457

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score 4 · Accepted Answer · edited Jan 08 '20 at 08:37

4

Compare by dates of last commits in all branches. ListMode.ALL can be changed to ListMode.REMOTE to compare only remote branches. Or... the fluent setter .setListMode(whatever) can be omitted to read from the local repository.

RevCommit youngestCommit = null;
Git git = new Git(repository);
List<Ref> branches = git.branchList().setListMode(ListMode.ALL).call();
try {
    RevWalk walk = new RevWalk(git.getRepository());
    for(Ref branch : branches) {
        RevCommit commit = walk.parseCommit(branch.getObjectId());
        if(youngestCommit == null || commit.getAuthorIdent().getWhen().compareTo(
           youngestCommit.getAuthorIdent().getWhen()) > 0)
           youngestCommit = commit;
    }
} catch (...)

edited Jan 08 '20 at 08:37

Nicolas

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answered Mar 15 '17 at 21:05

Grzegorz Górkiewicz

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Would it return the youngest commit by date in the whole repo regardless of the branches? – Master Mind Mar 15 '17 at 21:06
No, it will return the commit to which `HEAD` points to (usually the current branch). – Rüdiger Herrmann Mar 15 '17 at 21:21
The snippet assumes that the newest commit is among the branch heads, which may, at least in theory, not be the case. Or am I missing something? Another issue is that the author timestamp is compared. Use `getCommiterIdent().getWhen()` instead. – Rüdiger Herrmann Mar 17 '17 at 19:03

score 3 · Answer 3 · answered Aug 30 '17 at 08:13

Below you can find a Java 8 Stream API solution:

final List<Ref> branches = git.branchList().setListMode(ListBranchCommand.ListMode.ALL).call();
final RevWalk revWalk = new RevWalk(git.getRepository());

branches.stream()
        .map(branch -> {
            try {
                return revWalk.parseCommit(branch.getObjectId());
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        })
        .sorted(Comparator.comparing((RevCommit commit) -> commit.getAuthorIdent().getWhen()).reversed())
        .findFirst()
        .ifPresent(commit -> {
            System.out.printf("%s: %s (%s)%n", commit.getAuthorIdent().getWhen(), commit.getShortMessage(), commit.getAuthorIdent().getName());
        });

It iterates over all branches and picks recent commits in those branches, then it sorts list of commits by date in descendant order and picks the first one. If it exists it prints to console output something like this:

Wed Aug 30 09:49:42 CEST 2017: test file added (Szymon Stepniak)

Of course the behavior on last commit existence is exemplary and it can be easily replaced with any additional business logic. I hope it helps.

score 2 · Answer 4 · answered Mar 15 '17 at 21:26

To find the newest commit within a repository, configure a RevWalk to start from all known refs and sort it descending by commit date. For example:

Repository repo = ...
try( RevWalk revWalk = new RevWalk( repo ) ) {
  revWalk.sort( RevSort.COMMIT_TIME_DESC );
  Map<String, Ref> allRefs = repo.getRefDatabase().getRefs( RefDatabase.ALL );
  for( Ref ref : allRefs.values() ) {
    RevCommit commit = revWalk.parseCommit( ref.getLeaf().getObjectId() );
    revWalk.markStart( commit );
  }
  RevCommit newestCommit = revWalk.next();
}

Depending on your use case, you may also want to mark start points from refs from repo.getRefDatabase().getAdditionalRefs() which includes refs like FETCH_RESULT, ORIG_HEAD, etc. If you find that there are still untracked refs, use repo.getRefDatabase().getRef().

I don't get this. The loop over refs does nothing but overwrite the `RevWalk` starting point at each iteration. Why didn't you use the last ref instead? — Abhijit Sarkar, Oct 22 '20 at 06:56
`markStart` does not override but adds a starting point. After the `for` loop, the `RevWalk` is configured to sort commits by time and include commits from all refs returned by `getRefs(...)` — Rüdiger Herrmann, Oct 23 '20 at 12:22

Get the latest commit in a repository with JGit

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