git - Abort merge using JGit

Question

This is pretty straightforward: How do I simulate the command git merge --abort in JGit? I need to "preview" the conflicts prior to the real merge

Answer 1

There is no direct equivalent for git merge --abort in JGit. This code snippet may serve as a starting point:

// clear the merge state
repository.writeMergeCommitMsg(null);
repository.writeMergeHeads(null);

// reset the index and work directory to HEAD
Git.wrap(repository).reset().setMode(ResetType.HARD).call();

It empties the merge state files and then resets index and work directory to the contents of the current HEAD commit.

In order to test if two commits can be merged, you could also use an in-core merger. This would avoid checking out the conflicting commit into the work directory just to reset them later on.

RevCommit parentCommit = mergeCommit.getParent(0);
revWalk.parseHeaders(parentCommit);

ResolveMerger merger = (ResolveMerger) MergeStrategy.RESOLVE.newMerger(repository, true);
merger.setWorkingTreeIterator(new FileTreeIterator(repository));
merger.setBase(parentCommit.getTree());
if (!merger.merge(headCommit, mergeCommit)) {
  if (merger.failed()) {
    throw new IllegalStateException("Should not happen with in-core mergers");
  }
  // inspect merger.getMergeResults() for further details
}