Hook error when using commit-or-branch config

When using the config "commit-or-branch" the install or upgrade phases fail due to a non-existing discourse directory. The directory keeps changing at every run so it's not possible to bypass it by renaming the directory and trying again.

Trace:

2018-06-18 20:28:59 ERROR juju-log Hook error:
Traceback (most recent call last):
  File "/var/lib/juju/agents/unit-discourse-5/.venv/lib/python3.6/site-packages/charms/reactive/__init__.py", line 72, in main
    bus.dispatch(restricted=restricted_mode)
  File "/var/lib/juju/agents/unit-discourse-5/.venv/lib/python3.6/site-packages/charms/reactive/bus.py", line 382, in dispatch
    _invoke(other_handlers)
  File "/var/lib/juju/agents/unit-discourse-5/.venv/lib/python3.6/site-packages/charms/reactive/bus.py", line 358, in _invoke
    handler.invoke()
  File "/var/lib/juju/agents/unit-discourse-5/.venv/lib/python3.6/site-packages/charms/reactive/bus.py", line 180, in invoke
    self._action(*args)
  File "/var/lib/juju/agents/unit-discourse-5/charm/reactive/git_deploy.py", line 51, in git_deploy_avail
    update_to_commit(config('commit-or-branch'), deploy_dir=new_deploy_dir)
  File "lib/charms/layer/git_deploy.py", line 49, in update_to_commit
    res = check_call(git_pull, shell=True)
  File "/usr/lib/python3.6/subprocess.py", line 291, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command 'cd /srv/discourse/2018061820281518 && GIT_SSH=/var/lib/juju/agents/unit-discourse-5/charm/files/wrap_ssh.sh git pull' returned non-zero exit status 1.

2018-06-18 20:28:59 DEBUG install Traceback (most recent call last):
2018-06-18 20:28:59 DEBUG install File "/var/lib/juju/agents/unit-discourse-5/charm/hooks/install", line 19, in <module>
2018-06-18 20:28:59 DEBUG install main()
2018-06-18 20:28:59 DEBUG install File "/var/lib/juju/agents/unit-discourse-5/.venv/lib/python3.6/site-packages/charms/reactive/__init__.py", line 72, in main
2018-06-18 20:28:59 DEBUG install bus.dispatch(restricted=restricted_mode)
2018-06-18 20:28:59 DEBUG install File "/var/lib/juju/agents/unit-discourse-5/.venv/lib/python3.6/site-packages/charms/reactive/bus.py", line 382, in dispatch
2018-06-18 20:28:59 DEBUG install _invoke(other_handlers)
2018-06-18 20:28:59 DEBUG install File "/var/lib/juju/agents/unit-discourse-5/.venv/lib/python3.6/site-packages/charms/reactive/bus.py", line 358, in _invoke
2018-06-18 20:28:59 DEBUG install handler.invoke()
2018-06-18 20:28:59 DEBUG install File "/var/lib/juju/agents/unit-discourse-5/.venv/lib/python3.6/site-packages/charms/reactive/bus.py", line 180, in invoke
2018-06-18 20:28:59 DEBUG install self._action(*args)
2018-06-18 20:28:59 DEBUG install File "/var/lib/juju/agents/unit-discourse-5/charm/reactive/git_deploy.py", line 51, in git_deploy_avail
2018-06-18 20:28:59 DEBUG install update_to_commit(config('commit-or-branch'), deploy_dir=new_deploy_dir)
2018-06-18 20:28:59 DEBUG install File "lib/charms/layer/git_deploy.py", line 49, in update_to_commit
2018-06-18 20:28:59 DEBUG install res = check_call(git_pull, shell=True)
2018-06-18 20:28:59 DEBUG install File "/usr/lib/python3.6/subprocess.py", line 291, in check_call
2018-06-18 20:28:59 DEBUG install raise CalledProcessError(retcode, cmd)
2018-06-18 20:28:59 DEBUG install subprocess.CalledProcessError: Command 'cd /srv/discourse/2018061820281518 && GIT_SSH=/var/lib/juju/agents/unit-discourse-5/charm/files/wrap_ssh.sh git pull' returned non-zero exit status 1.
2018-06-18 20:28:59 ERROR juju.worker.uniter.operation runhook.go:113 hook "install" failed: exit status 1
2018-06-18 20:28:59 INFO juju.worker.uniter resolver.go:100 awaiting error resolution for "install" hook