Multiple Overlapping Wildcard RefSpecs Incorrectly Prune Up-to-Date Refs

[janikmueller]

Version

6.8.0

Operating System

MacOS

Bug description

When using multiple wildcard refspecs that map to the same destination pattern with setRemoveDeletedRefs(true), JGit incorrectly prunes refs that are:

1. Advertised by the remote server
2. Already up-to-date (local SHA == remote SHA)
3. Matching the wildcard destination pattern

This causes refs to alternate between created and deleted on subsequent fetches.

Actual behavior

Run 1:

• Remote advertises: refs/merge-requests/42/head → abc123
• RefSpec 2 matches and creates: refs/remotes/merge-requests/42/head → abc123
• TrackingRefUpdate status: NEW ✓

Run 2 (unchanged remote):

• Remote advertises: refs/merge-requests/42/head → abc123 (same SHA)
• RefSpec 1: Match, but up-to-date (not added to TrackingRefUpdates)
• RefSpec 2: No match (checks refs/merge-requests/*/from)
• Prune logic: "Local ref refs/remotes/merge-requests/42/head wasn't updated by ANY refspec → must be deleted!"
• TrackingRefUpdate status: FORCED to 00000000... ✗
• Result: ALL REFS DELETED ✗

Run 3:

• Same as Run 1 - refs recreated
• Pattern repeats: create → delete → create → delete...

Expected behavior

When fetching with multiple wildcard refspecs like +refs/merge-requests/*/head:refs/remotes/merge-requests/*/head and +refs/merge-requests/*/from:refs/remotes/merge-requests/*/head:

Run 1:

• Remote advertises: refs/merge-requests/42/head → abc123
• RefSpec matches and creates: refs/remotes/merge-requests/42/head → abc123
• Result: Ref created ✓

Run 2 (unchanged remote):

• Remote advertises: refs/merge-requests/42/head → abc123 (same SHA)
• Local has: refs/remotes/merge-requests/42/head → abc123 (up-to-date)
• Result: No changes, ref remains ✓

Run 3:

• Result: Still stable ✓

Relevant log output

Other information

Impact

Affects any application using JGit with:

• Multiple wildcard refspecs mapping to the same destination
• Pruning enabled
• Real-world use case: Cross-platform merge request/pull request support (GitHub + GitLab + others)

Minimal reproduction example:

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Arrays;
import java.util.Collection;
import java.util.Comparator;

import org.eclipse.jgit.api.Git;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.transport.FetchResult;
import org.eclipse.jgit.transport.RefSpec;
import org.eclipse.jgit.transport.TrackingRefUpdate;

public class JGitWildcardPruneBug {

    public static void main(String[] args) throws Exception {
        String remoteUrl = "https://gitlab.com/gitlab-org/gitlab-runner.git";

        try (TempDirectory tempDir = new TempDirectory("jgit-bug-test")) {
            try (Git git = Git.cloneRepository().setURI(remoteUrl).setDirectory(tempDir.getPath().toFile())
                    .setCloneAllBranches(false).call()) {

                // Add MULTIPLE refspecs that overlap in destination
                RefSpec wildcardRefSpec1 = new RefSpec("+refs/merge-requests/*/head:refs/merge-requests/*/head");
                RefSpec wildcardRefSpec2 = new RefSpec("+refs/merge-requests/*/from:refs/merge-requests/*/head");

                for (int run = 1; run <= 3; run++) {
                    System.out.println("=== RUN " + run + " ===");

                    FetchResult result1 = git.fetch().setRefSpecs(Arrays.asList(wildcardRefSpec1, wildcardRefSpec2))
                            .setRemoveDeletedRefs(true).call();
                    printFetchResult(result1);

                    printLocalMergeRequestRefs(git, "AFTER RUN " + run);
                    System.out.println();
                }
            }
        }
    }

    private static void printFetchResult(FetchResult result) {
        Collection<TrackingRefUpdate> updates = result.getTrackingRefUpdates();
        long mrUpdates = updates.stream().filter(u -> u.getLocalName().contains("merge-requests")).count();

        if (mrUpdates > 0) {
            System.out.println(" - MR ref updates: " + mrUpdates);
            updates.stream().filter(u -> u.getLocalName().contains("merge-requests")).limit(3).forEach(update -> {
                System.out.printf("    %s: %s -> %s (%s)%n", update.getLocalName(),
                        update.getOldObjectId().abbreviate(7).name(), update.getNewObjectId().abbreviate(7).name(),
                        update.getResult());
            });
            if (mrUpdates > 3) {
                System.out.println("    ... (" + (mrUpdates - 3) + " more)");
            }
        } else {
            System.out.println(" - No MR ref updates");
        }
    }

    private static void printLocalMergeRequestRefs(Git git, String label) throws Exception {
        Collection<Ref> refs = git.getRepository().getRefDatabase().getRefs();
        long mrCount = refs.stream().filter(ref -> ref.getName().contains("merge-requests")).count();

        System.out.println(label + " - Local MR refs: " + mrCount);
        if (mrCount == 0) {
            System.out.println("ALL MERGE REQUEST REFS WERE DELETED!");
        }
    }

    static class TempDirectory implements AutoCloseable {

        private final Path path;

        public TempDirectory(String prefix) throws IOException {
            this.path = Files.createTempDirectory(prefix);
        }

        public Path getPath() {
            return path;
        }

        @Override
        public void close() throws IOException {
            if (Files.exists(path)) {
                Files.walk(path).sorted(Comparator.reverseOrder()).map(Path::toFile).forEach(File::delete);
            }
        }
    }
}

Expected Output

=== RUN 1 ===

• MR ref updates: 1720
  refs/merge-requests/1004/head: 0000000 -> f4a3dad (NEW)
  refs/merge-requests/1005/head: 0000000 -> 5ac68e9 (NEW)
  refs/merge-requests/1006/head: 0000000 -> 88ff5e7 (NEW)
  ... (1717 more)
  AFTER RUN 1 - Local MR refs: 1720

=== RUN 2 ===

• No MR ref updates
  AFTER RUN 2 - Local MR refs: 1720

=== RUN 3 ===

• No MR ref updates
  AFTER RUN 3 - Local MR refs: 1720

Actual Output

=== RUN 1 ===

• MR ref updates: 1720
  refs/merge-requests/1004/head: 0000000 -> f4a3dad (NEW)
  refs/merge-requests/1005/head: 0000000 -> 5ac68e9 (NEW)
  refs/merge-requests/1006/head: 0000000 -> 88ff5e7 (NEW)
  ... (1717 more)
  AFTER RUN 1 - Local MR refs: 1720

=== RUN 2 ===

• MR ref updates: 1720
  refs/merge-requests/1004/head: f4a3dad -> 0000000 (FORCED)
  refs/merge-requests/1005/head: 5ac68e9 -> 0000000 (FORCED)
  refs/merge-requests/1006/head: 88ff5e7 -> 0000000 (FORCED)
  ... (1717 more)
  AFTER RUN 2 - Local MR refs: 0
  ALL MERGE REQUEST REFS WERE DELETED!

=== RUN 3 ===

• MR ref updates: 1720
  refs/merge-requests/1004/head: 0000000 -> f4a3dad (NEW)
  refs/merge-requests/1005/head: 0000000 -> 5ac68e9 (NEW)
  refs/merge-requests/1006/head: 0000000 -> 88ff5e7 (NEW)
  ... (1717 more)
  AFTER RUN 3 - Local MR refs: 1720

[janikmueller]

Addition:
The bug exists also in the latest release version (v7.4.0.202509020913-r). Fix version line could be 6.8 or 7.4.