git-sync: Can't work when use secretRef on Kubernetes.

apiVersion: v1
kind: Secret
metadata:
name: git-credentials
data:
    GIT_SYNC_USERNAME: <base64_encoded_git_username>
    GIT_SYNC_PASSWORD: <base64_encoded_git_password>

- name: GIT_SYNC_USERNAME
  valueFrom:
    secretKeyRef:
       name: {{ .Values.dags.gitSync.credentialsSecret | quote }}
       key: GIT_SYNC_USERNAME
- name: GIT_SYNC_PASSWORD
  valueFrom:
    secretKeyRef:
       name: {{ .Values.dags.gitSync.credentialsSecret | quote }}
       key: GIT_SYNC_PASSWORD

git-sync can not work with this kind of env.

Cloning into '/dags'...\nfatal: could not read Username for 'https://xxxxxx': No such device or address