Update release instructions (#348)

* Update release instructions

This was necessary after permission changes due to the
repository migration to kubernetes-sigs.

* Review comments and remove more outdated instructions

* Add note to update the krew-index CI pipeline

Author: corneliusweig

docs/RELEASING_KREW.md

@@ -29,7 +29,7 @@ Krew tags versions starting with `v`. Example: `v0.2.0-rc.1`.
 1. **Decide on a version number:** set it to `$TAG` variable:
 
     ```sh
-    TAG=v0.2.0-rc.1 # <- change this
+    TAG=v0.3.2-rc.1 # <- change this
     ```
 
 1. **Update installation instructions:** Version number is hardcoded in
@@ -39,9 +39,15 @@ Krew tags versions starting with `v`. Example: `v0.2.0-rc.1`.
 
        git commit -am "Release ${TAG:?TAG required}"
 
+1. **Push PR and merge changes**: The repository hooks forbid direct pushes to
+   master, so the changes from the previous step need to be pushed and merged
+   as a regular PR.
+
 1. **Tag the release:**
 
     ```sh
+    git fetch origin
+    git reset --hard origin/master    # when the previous merge is done
     release_notes="$(TAG=$TAG hack/make-release-notes.sh)"
     git tag -a "${TAG:?TAG required}" -m "${release_notes}"
     ```
@@ -52,19 +58,22 @@ Krew tags versions starting with `v`. Example: `v0.2.0-rc.1`.
 
 1. **Push the tag:**
 
-       git push --follow-tags
-
-    Due to branch restrictions on GitHub preventing pushing to a branch
-    directly, this command may require `-f`.
+       git push --tags
 
 1. **Verify on Releases tab on GitHub**
 
-1. **Make the new version available on krew index:** Copy the `krew.yaml` from
-   the release artifacts and make a pull request to
+1. **Make the new version available on krew index:** Get the latest `krew.yaml` from
+
+       curl -LO https://github.com/kubernetes-sigs/krew/releases/download/v0.3.2-rc.1/krew.yaml
+
+   and make a pull request to
    [krew-index](https://github.com/kubernetes-sigs/krew-index/) repository.
    This will make the plugin available to upgrade for users using older versions
    of krew.
 
+1. **Update krew-index CI**: For validating manifests, the CI should use the latest version
+   (see `.travis.yml` in `krew-index` the repository).
+
 ## Release artifacts
 
 When a tag is pushed to the repository, Travis CI will make a release on GitHub