RELEASING.md: Update doc with releasetool usage
-# How to Release this Repo
-
-1. Determine the current release version with `git tag -l`. It should look
- something like `vX.Y.Z`. We'll call the current
- version `$CV` and the new version `$NV`.
-1. On master, run `git log $CV..` to list all the changes since the last
- release.
-1. Edit `CHANGES.md` to include a summary of the changes.
-1. Mail the CL containing the `CHANGES.md` changes. When the CL is approved, submit it.
-1. Without submitting any other CLs:
- a. Switch to master.
- b. Tag the repo with the next version: `git tag $NV`.
- c. Push the tag: `git push origin $NV`.
+# How to Create a New Release
+
+## Prerequisites
+
+- Install [releasetool](https://github.com/googleapis/releasetool).
+- Add `github` as as git remote:
+ ```
+ git remote add git@github.com:GoogleCloudPlatform/google-cloud-go.git
+ ```
+
+## Create a release
+
+1. `cd` into the root directory, e.g., `~/go/src/cloud.google.com/go`
+1. Checkout the master branch and ensure a clean and up-to-date state.
+ ```
+ git checkout master
+ git pull --tags origin master
+ ```
+1. Run releasetool to generate a changelog from the last version. Note,
+ releasetool will prompt if the new version is a major, minor, or patch
+ version.
+ ```
+ releasetool start --language go
+ ```
+1. Format the output to match CHANGES.md.
+1. Submit a CL with the changes in CHANGES.md. The commit message should look
+ like this (where `v0.31.0` is instead the correct version number):
+ ```
+ all: Release v0.31.0
+ ```
+1. Wait for approval from all reviewers and then submit the CL.
+1. Return to the master branch and pull the release commit.
+ ```
+ git checkout master
+ git pull origin master
+ ```
+1. Tag the current commit with the new version (e.g., `v0.31.0`)
+ ```
+ releasetool tag --language go
+ ```
+1. Publish the tag to GoogleSource (i.e., origin):
+ ```
+ git push origin $NEW_VERSION
+ ```
+1. Visit the [releases page][releases] on GitHub and click the "Draft a new
+ release" button. For tag version, enter the tag published in the previous
+ step. For the release title, use the version (e.g., `v0.31.0`). For the
+ description, copy the changes added to CHANGES.md.
+
+
+[releases]: https://github.com/GoogleCloudPlatform/google-cloud-go/releases
