GIT_DEPTH specified per env. in gitlab-runner configuration doesn't work.

Summary

variable GIT_DEPTH specified in gitlab-runner configuration file (config.toml) doesn't apply. I've been following this part of gitlab docs.

https://docs.gitlab.com/ee/ci/large_repositories/

Steps to reproduce

add GIT_DEPTH variable into config.toml as described in docs.

What is the current bug behavior?

GIT_DEPTH has the default value(50)

What is the expected correct behavior?

GIT_DEPTH value will apply per project if specified in gitlab runner config.toml

Results of GitLab environment info

Expand for output related to GitLab environment info

System information
System:        
Proxy:        no
Current User:    git
Using RVM:    no
Ruby Version:    2.6.3p62
Gem Version:    2.7.9
Bundler Version:1.17.3
Rake Version:    12.3.2
Redis Version:    3.2.12
Git Version:    2.22.0
Sidekiq Version:5.2.7
Go Version:    unknownGitLab information
Version:    12.2.1-ee
Revision:    e4a8b6c773a
Directory:    /opt/gitlab/embedded/service/gitlab-rails
DB Adapter:    PostgreSQL
DB Version:    10.7
URL:        https://gitlab.mgmt.gl.drmax.net
HTTP Clone URL:    https://gitlab.mgmt.gl.drmax.net/some-group/some-project.git
SSH Clone URL:    git@gitlab.mgmt.gl.drmax.net:some-group/some-project.git
Elasticsearch:    no
Geo:        no
Using LDAP:    no
Using Omniauth:    yes
Omniauth Providers:GitLab Shell
Version:    9.3.0
Repository storage paths:
- default:     /var/opt/gitlab/git-data/repositories
GitLab Shell path:        /opt/gitlab/embedded/service/gitlab-shell
Git:        /opt/gitlab/embedded/bin/git

Results of GitLab application Check

Checking GitLab subtasks ...Checking GitLab Shell ...GitLab Shell: ... GitLab Shell version >= 9.3.0 ? ... OK (9.3.0)
Running /opt/gitlab/embedded/service/gitlab-shell/bin/check
Check GitLab API access: OK
Redis available via internal API: OKAccess to /var/opt/gitlab/.ssh/authorized_keys: OK
gitlab-shell self-check successfulChecking GitLab Shell ... FinishedChecking Gitaly ...Gitaly: ... default ... OKChecking Gitaly ... FinishedChecking Sidekiq ...Sidekiq: ... Running? ... yes
Number of Sidekiq processes ... 1Checking Sidekiq ... FinishedChecking Incoming Email ...Incoming Email: ... Reply by email is disabled in config/gitlab.ymlChecking Incoming Email ... FinishedChecking LDAP ...LDAP: ... LDAP is disabled in config/gitlab.ymlChecking LDAP ... FinishedChecking GitLab App ...Git configured correctly? ... yes
Database config exists? ... yes
All migrations up? ... yes
Database contains orphaned GroupMembers? ... no
GitLab config exists? ... yes
GitLab config up to date? ... yes
Log directory writable? ... yes
Tmp directory writable? ... yes
Uploads directory exists? ... yes
Uploads directory has correct permissions? ... yes
Uploads directory tmp has correct permissions? ... yes
Init script exists? ... skipped (omnibus-gitlab has no init script)
Init script up-to-date? ... skipped (omnibus-gitlab has no init script)
Projects have namespace: ...19/3059 ... yes
Redis version >= 2.8.0? ... yes
Ruby version >= 2.5.3 ? ... yes (2.6.3)
Git version >= 2.22.0 ? ... yes (2.22.0)
Git user has default SSH configuration? ... yes
Active users: ... 3
Elasticsearch version 5.6 - 6.x? ... skipped (elasticsearch is disabled)Checking GitLab App ... FinishedChecking GitLab subtasks ... Finished