docs: How to deploy development build

docs/how-to-deploy-dev-build.md

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+# How to deploy development build of image registry
+
+## Prerequisites
+
+ * An OpenShift cluster.
+ * Credentials from [the app.ci cluster](https://console-openshift-console.apps.ci.l2s4.p1.openshiftapps.com/).
+ * A public image repository (for example, you can create a public repository on [quay.io](https://quay.io/)).
+
+## Logging into the app.ci cluster and its registry
+
+1. Copy the login command from <https://console-openshift-console.apps.ci.l2s4.p1.openshiftapps.com/> and run it
+2. Rename the context for the `app.ci` cluster
+
+    ```
+    oc config rename-context "$(oc config current-context)" app.ci
+    ```
+
+3. Login into the registry `registry.ci.openshift.org`
+
+    ```
+    oc --context=app.ci whoami -t | docker login -u unused --password-stdin "$(oc --context=app.ci registry info --public=true)"
+    ```
+
+## Switching the image registry operator into the Unmanaged mode
+
+1. You'll need to change the image registry deployment manually, so disable the image registry operator
+
+    ```
+    oc patch configs.imageregistry cluster --type=merge -p '{"spec":{"managementState":"Unmanaged"}}'
+    ```
+
+## Building and deploying a new container image
+
+1. Go to the directory with the image registry sources
+
+    ```
+    cd ./openshift/image-registry
+    ```
+
+2. Build a new image
+
+    ```
+    docker build -f Dockerfile.rhel7 -t quay.io/rh-obulatov/image-registry .
+    ```
+
+3. Push the new image
+
+    ```
+    docker push quay.io/rh-obulatov/image-registry
+    ```
+
+4. Deploy the new build
+
+    ```
+    oc -n openshift-image-registry set image deploy/image-registry registry="$(docker inspect --format='{{index .RepoDigests 0}}' quay.io/rh-obulatov/image-registry)"
+    ```
+
+5. Wait until the pods use the new image
+
+    ```
+    oc -n openshift-image-registry get pods -l docker-registry=default -o custom-columns="NAME:.metadata.name,STATUS:.status.phase,IMAGE:.spec.containers[0].image"
+    ```
+
+6. Enjoy your registry!