Update JSON 6902 patch for compatibility with older kubectl

The inline patch technique only works on kubectl v1.21.0 and
later. While it is certainly much more convenient to write it
out in that manner, this uses the previously available technique
of referencing the location of a patch file to apply a patch,
thus ensuring greater compatibility.

Author: Jonathan S. Katz

kustomize/install/bases/kustomization.yaml

@@ -21,8 +21,12 @@ patchesJson6902:
       version: v1
       kind: Deployment
       name: pgo
-    patch: |-
-      - op: remove
-        path: /spec/selector/matchLabels/app.kubernetes.io~1name
-      - op: remove
-        path: /spec/selector/matchLabels/app.kubernetes.io~1version
+    path: ./patches/selectors.yaml
+    # path is used for compatibility with version of kubectl prior to v1.21.0.
+    # newer version of kubectl can use the inline patch below, which is the
+    # preferred method going forward.
+    # patch: |-
+    #   - op: remove
+    #     path: /spec/selector/matchLabels/app.kubernetes.io~1name
+    #   - op: remove
+    #     path: /spec/selector/matchLabels/app.kubernetes.io~1version

kustomize/install/bases/patches/selectors.yaml

@@ -0,0 +1,4 @@
+- op: remove
+  path: /spec/selector/matchLabels/app.kubernetes.io~1name
+- op: remove
+  path: /spec/selector/matchLabels/app.kubernetes.io~1version