Previous to the update of the git plugin everything was working fine (with Git plugin version 3.4.1).

After updating to version 3.5.0 now I am not able to build neither merque-requests nor tags, I only see regular branches from the repository (GitLab by the way).

I've been looking changes made in the code, more precisely changes made in

src/main/java/jenkins/plugins/git/AbstractGitSCMSource.java

There has been a major change in the way branches are discovered (that can be seen in the function "discoverBranches"):

• 3.4.1 - In this version, "client.getRemoteBranches" is used, which I guess, corresponds to a "git branch -r". Then it parses the output to get the names of the branches.
• 3.5.0 - In this version, "client.getRemoteReferences" is used, that corresponds to a "git ls-remote -h". Then, it parses the output to get the names of the branches.

I've set "Specify ref specs" with the needed values to be able to fetch  the merge-requests and the tags ('+refs/merge-requests//head:refs/remotes/origin/merge-requests/' and '+refs/tags/:refs/remotes/origin/tags/').

If I perform manually both operations ("git branch -r" and "git ls-remote -h") the output is not the same:

$ git branch -r
origin/HEAD -> origin/master

origin/feature/generic-tag-attribute
origin/merge-requests/1
origin/merge-requests/2
origin/merge-requests/3
origin/tags/v1.5.0-alpha.0

and

$ git ls-remote -h 
From http:/**********
2c26dca25a748017ff52b22d81c549506abc12be refs/heads/feature/generic-tag-attribute
1f43ef826799500cb585273eca3517c8a5eb026a refs/heads/master

In the first example (mimics Git plugin 3.4.1) I get merge-requests and tags, in the second (mimics 3.5.0) I don't.