I fail to install GitLab shell, which is an SSH access and repository management software for GitLab

I fail to install the Gitlab shell. This is how it looks like:

$ sudo -u git -H bundle exec rake gitlab:shell:install[v1.9.4] REDIS_URL=redis://localhost:6379 RAILS_ENV=production

git fetch origin && git reset --hard $(git describe v1.9.4 || git describe origin/v1.9.4)
fatal: Not a git repository (or any of the parent directories): .git
rake aborted!
Command failed with status (128): [git fetch origin && git reset --hard $(git...]
/home/git/gitlab/lib/tasks/gitlab/shell.rake:24:in `block (4 levels) in <top (required)>'
/home/git/gitlab/lib/tasks/gitlab/shell.rake:23:in `chdir'
/home/git/gitlab/lib/tasks/gitlab/shell.rake:23:in `block (3 levels) in <top (required)>'
Tasks: TOP => gitlab:shell:install
(See full trace by running task with --trace)

Any ideas how to fix it?