Move template-sync sidecar to datahub secrets

We override `hub.extraContainers` in `secrets/staging.yaml`
and `secrets/prod.yaml` to include the fetch-course-emails
container along the hub. But this overrides what's in
`config/common.yaml` destructively, since it just replaces
the list rather than add to it.

I've filed jupyterhub/kubespawner#468
to fix this. Until then, I've manually moved the extraContainers
config to the secret files.

deployments/datahub/config/common.yaml

@@ -13,6 +13,9 @@ jupyterhub:
     nodeSelector:
       hub.jupyter.org/pool-name: core-pool
     initContainers:
+      # There's another sidecar, specified in `secrets/staging.yaml` and `secrets/prod.yaml`
+      # that keeps this up to date. https://github.com/jupyterhub/kubespawner/issues/468
+      # should help us move that back here.
       - name: templates-clone
         image: alpine/git
         args:
@@ -29,25 +32,6 @@ jupyterhub:
         volumeMounts:
           - name: custom-templates
             mountPath: /srv/repo
-    extraContainers:
-      # Keep templates in sync, so you can autodeploy from master
-      - name: templates-sync
-        image: alpine/git
-        workingDir: /srv/repo
-        command:
-          - /bin/sh
-        args:
-          - -c
-          # Do git reset --hard origin/master so we aren't confused by force pushes
-          - "while true; do git fetch origin; git reset --hard origin/master; sleep\
-            \ 5m; done"
-        securityContext:
-          runAsUser: 1000
-          allowPrivilegeEscalation: false
-          readOnlyRootFilesystem: true
-        volumeMounts:
-          - name: custom-templates
-            mountPath: /srv/repo
     extraVolumes:
       - name: custom-templates
         emptyDir: {}