update release instructions (#245)

docs/maintaining.md

@@ -10,6 +10,15 @@ Cloud Agent.
 Each maintainer performing a release should perform the following steps once
 before releasing the Grafana Cloud Agent.
 
+#### Prerelease testing 
+
+For testing a release, run the [K3d example](../example/k3d/README.md) locally.
+Let it run for about 90 minutes, keeping an occassional eye on the Agent
+Operational dashboard (noting that metrics from the scraping service will take
+time to show up). After 90 minutes, if nothing has crashed and you see metrics
+for both the scraping service and the non-scraping service, the Agent is ready
+for release. 
+
 #### Add Existing GPG Key to GitHub
 
 First, Navigate to your user's [SSH and GPG keys settings
@@ -49,8 +58,7 @@ export GPG_TTY=$(tty)
 1. Create a new branch to update `CHANGELOG.md` and references to version
    numbers across the entire repository (e.g. README.md in the project root).
 2. Modify `CHANGELOG.md` with the new version number and its release date.
-3. List all the merged PRs since the previous release. This command is helpful
-   for generating the list (modifying the date to the date of the previous release): `curl https://api.github.com/search/issues?q=repo:grafana/agent+is:pr+"merged:>=2019-08-02" | jq -r ' .items[] | "* [" + (.number|tostring) + "](" + .html_url + ") **" + .user.login + "**: " + .title'`
+3. Add a new section in `CHANGELOG.md` for `Master (unreleased)`.
 4. Go through the entire repository and find references to the previous release
    version, updating them to reference the new version.
 5. Run `make example-kubernetes` and `make example-dashboards` to update
@@ -86,6 +94,8 @@ After this final set of steps, you can publish your draft!
    to feel more comfortable with it.
 4. Publish the release!
 
+The release isn't done yet! Keep reading for the final step.
+
 ## Updating Release Branch
 
 The `release` branch should always point at the SHA of the commit of the latest