Merge pull request kubernetes-sigs#5440 from nrb/doc-prev-tag-calculation

🌱 Document how previous versions are found

Author: k8s-ci-robot

.github/workflows/release.yaml

@@ -24,7 +24,9 @@ jobs:
       - name: Set version info
         run: |
           echo "VERSION=${GITHUB_REF_NAME}" >> $GITHUB_ENV
-          echo "PREVIOUS_VERSION=$(git describe --abbrev=0 2> /dev/null)" >> $GITHUB_ENV
+          # NB: this gets the closest tag cut from the same branch; for new minor tags, it will find the previous minor, not the previous patch release
+          # (for example v2.7.0, not v2.7.3). For new patch releases, it should fetch the previous patch (e.g. 2.7.3, not v2.7.0)
+          echo "PREVIOUS_VERSION=$(git describe --abbrev=0 2> /dev/null)" >> $GITHUB_ENV 
           echo "RELEASE_BRANCH=release-$(echo ${GITHUB_REF_NAME} | grep -Eo '[0-9]\.[0-9]+')" >> $GITHUB_ENV
           echo "RELEASE_TAG=${GITHUB_REF_NAME}" >> $GITHUB_ENV
       - name: Run release