Get latest tag in branch with JGit

I am trying to get the JGit equivalent of the command

git describe --match "[0-9]*.[0-9]*.[0-9]*" --abbrev=0 --tags $(git rev-list --tags --branches=master --max-count=1)

I have tried getting all the tags in the project and then finding the greatest tag in the branch via the BranchListCommand, but that is to slow.

I am stuck and I cannot find anything that help via my searches.

Does anyone have any idea how to do the intended result?

Answer

You can fetch all tags and then walk the commits on the branch and check for each commit if there is a tag for this ref.

i.e. fetch all tags via:

git.tagList().call()

then fetch all commits of the branch via:

git.log().add(repository.resolve(BRANCH)).call()

And then for each commit check if a tag exists at this ref.

When run on a fairly large repository on a branch with more than 60k commits, walking all the commits this way is done in 1.2 seconds.

Had 60843 commits overall on branch remotes/origin/master, iteration took 1200ms

An even larger branch takes 8 seconds when walking 380k commits.

Had 388613 commits overall on branch remotes/origin/master, iteration took 8261ms

I have added a ready-to-run snippet to the jgit-cookboot, see ListTagsOnBranch.java