SubGit calling GitLabs post-receive hook doesn't work

Question

We are trying a soft migration from svn to git (GitLab) using SubGit as mirror. All works fine, except that commits to the svn repo do not trigger the GitLabs post-recive hook correctly (I suppose).

The commit in the git repo is there, but the activity stream does not get updated afterwards, the CI pipeline does not get triggered and so on.

I can see that the post-receive hook is called from SubGit:

[daemon][20] Executing [/var/opt/gitlab/git-
data/repositories/repo.git/hooks/post-receive]; environmentVariables=
{SVN_LAST_FETCHED_REVISION=33957, GIT_DIR=., GL_ID=user-
1};workingDirectory=/var/opt/gitlab/git-data/repositories/repo.git

(I replaced the real group/project name with repo)

The Sidekiq logs tells me there is some problem with a GL Repository:

WARN: ArgumentError: Invalid GL Repository "/var/opt/gitlab/git-
data/repositories/repo.git"

thrown in gitlab-rails/lib/gitlab/gl_repository.rb:10:

def self.parse(gl_repository)
  match_data = /\A(project|wiki)-([1-9][0-9]*)\z/.match(gl_repository)
  unless match_data
    raise ArgumentError, "Invalid GL Repository \"#{gl_repository}\""
  end

Grepping through the code it seems that the hook itself uses a GL_REPOSITORY environment variable that is not set by SubGit.

I tried calling the hook manually and setting GL_REPOSITORY to something that fulfill the regexp above ("project-13", 13 is the project id for this repo), but that leads to the a Ambiguous lookup - OID prefix is too short exception. (My fault, that would have worked if I had used correct hook data)

So, what is the GL_REPOSITORY environment variable, and how can I make SubGit set it?

I'm using:

• GitLab 9.4.5
• SubGit 3.2.5

Update:

I found out that GL_REPOSITORY ist just a string project-<GitLabDBProjectId>. For now i placed a text file with the correct string in every repository, and adjusted the post-receive hook itself to read out that file and use it as content instead of the GL_REPOSITORY variable.

There was some heavy reworking in GitLab relating to the project identifiers, and it seems that SubGit didn't catch up with that changes (Bug report exists).