use the correct versions to regen the japicmp files (#6451)

.github/workflows/generate-post-release-pr.yml

@@ -30,19 +30,20 @@ jobs:
       - name: Set environment variables
         run: |
           version=$(.github/scripts/get-version.sh)
-          if [[ $version =~ ^([0-9]+)\.([0-9]+)\.0$ ]]; then
+          echo "VERSION=$version" >> $GITHUB_ENV
+          prior_version=$(.github/scripts/get-prior-version.sh)
+          echo "PRIOR_VERSION=$prior_version" >> $GITHUB_ENV
+          if [[ $prior_version =~ ^([0-9]+)\.([0-9]+)\.([0-9]+)$ ]]; then
             major="${BASH_REMATCH[1]}"
             minor="${BASH_REMATCH[2]}"
-            next_version="$major.$((minor + 1)).0"
+            patch="${BASH_REMATCH[3]}"
+            
+            two_releases_ago="$major.$((minor - 1)).$patch"
           else
-            echo "unexpected version: $version"
+            echo "unexpected prior version: $prior_version"
             exit 1
           fi
-          echo "NEXT_VERSION=$next_version" >> $GITHUB_ENV
-          echo "VERSION=$version" >> $GITHUB_ENV
-          prior_version=$(.github/scripts/get-prior-version.sh)
-          echo "PRIOR_VERSION=$prior_version" >> $GITHUB_ENV
-
+          echo "TWO_VERSIONS_AGO=$two_releases_ago" >> $GITHUB_ENV
       - name: Use CLA approved github bot
         run: .github/scripts/use-cla-approved-github-bot.sh
 
@@ -51,13 +52,13 @@ jobs:
           # not using secrets.GITHUB_TOKEN since pull requests from that token do not run workflows
           GH_TOKEN: ${{ secrets.OPENTELEMETRYBOT_GITHUB_TOKEN }}
         run: |
-          ./gradlew updateVersionInDocs -Prelease.version=$VERSION
-          ./gradlew japicmp -PapiBaseVersion=$PRIOR_VERSION -PapiNewVersion=$VERSION
+          ./gradlew updateVersionInDocs -Prelease.version=$PRIOR_VERSION
+          ./gradlew japicmp -PapiBaseVersion=$TWO_VERSIONS_AGO -PapiNewVersion=$PRIOR_VERSION
           ./gradlew --refresh-dependencies japicmp
    
-          message="Post release for version $VERSION"
-          body="Post-release updates for version \`$VERSION\`."
-          branch="opentelemetrybot/post-release-for-${VERSION}"
+          message="Post release for version $PRIOR_VERSION"
+          body="Post-release updates for version \`$PRIOR_VERSION\`."
+          branch="opentelemetrybot/post-release-for-${PRIOR_VERSION}"
 
           git checkout -b $branch
           git commit -a -m "$message"