fix: package should use old dylibs based on tags

.github/workflows/_25_package.yml

@@ -8,6 +8,7 @@ on:
 
 env:
   FORCE_COLOR: 1
+  BRANCH_NAME: ${{ github.head_ref || github.ref_name }}
 
 jobs:
   packages:
@@ -25,18 +26,110 @@ jobs:
     steps:
       - name: Checkout 🛒
         uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11
+        with:
+          fetch-depth: 0
 
       - name: Download binaries from same run 📥
         uses: actions/download-artifact@9bc31d5ccc31df68ecc42ccf4149144866c47d8a
         with:
           name: chainflip-backend-bin
           path: ./target/release
 
-      - name: Download latest release binaries
+      # Pull requests to release should use the same rules as the release branch itself
+      # For simplicity we use the same rules for branches to main, since it doesn't matter if we use "main" as the branch name.
+      - name: Set branch name
+        id: set-branch-name
+        run: |
+          echo "Working branch name: ${{ env.BRANCH_NAME }}"
+          echo "Github event name: ${{ github.event_name }}"
+          if [ "${{ github.event_name }}" = "push" ]; then
+            echo "push"
+            echo "TARGET_BRANCH=${{ github.ref_name }}" >> $GITHUB_ENV
+          elif [ "${{ github.event_name }}" = "pull_request" ]; then
+            echo "pull or merge_group"
+            echo ${{ github.base_ref}}
+            echo "TARGET_BRANCH=${{ github.base_ref }}" >> $GITHUB_ENV
+          fi
+
+      - name: Is the branch a release/x.y branch?
+        shell: bash
+        run: |
+          echo "TARGET_BRANCH: ${{ env.TARGET_BRANCH }}"
+          TARGET_BRANCH=${{ env.TARGET_BRANCH }}
+          echo "Checking if branch name $TARGET_BRANCH is a release branch"
+          if [[ "${TARGET_BRANCH}" =~ ^release/[0-9]+\.[0-9]+$ ]]; then
+            echo "Branch name ${TARGET_BRANCH} does match the required format 'release/x.y'"
+            echo "IS_RELEASE_BRANCH=true" >> $GITHUB_ENV
+          else
+            echo "Branch name ${TARGET_BRANCH} does NOT match the required format 'release/x.y."
+            echo "IS_RELEASE_BRANCH=false" >> $GITHUB_ENV
+          fi
+
+      - name: Extract version and compute previous version
+        id: extract_version
+        if: env.IS_RELEASE_BRANCH == 'true'
+        shell: bash
+        run: |
+          git config --global --add safe.directory '*'
+
+          TARGET_BRANCH=${{ env.TARGET_BRANCH }}
+          VERSION=${TARGET_BRANCH#release/}
+          MAJOR=$(echo $VERSION | cut -d. -f1)
+          MINOR=$(echo $VERSION | cut -d. -f2)
+
+          # Compute the previous version
+          if [ $MINOR -eq 0 ]; then
+            PREV_MAJOR=$((MAJOR - 1))
+            if [ $PREV_MAJOR -ge 0 ]; then
+              PREV_VERSION="${PREV_MAJOR}"
+            else
+              echo "No previous version available"
+              exit 1
+            fi
+          else
+            PREV_MINOR=$((MINOR - 1))
+            PREV_VERSION="${MAJOR}.${PREV_MINOR}"
+          fi
+
+          echo "Previous version: $PREV_VERSION"
+
+          if [[ "$PREV_VERSION" == *.* ]]; then
+            # Find the highest tag matching the previous minor version prefix
+            HIGHEST_TAG=$(git tag -l "${PREV_VERSION}.*" | sort -V | tail -n 1)
+          else
+            # Find the highest tag for the previous major version
+            HIGHEST_TAG=$(git tag -l "${PREV_VERSION}.*.*" | sort -V | tail -n 1)
+          fi
+
+          if [ -z "$HIGHEST_TAG" ]; then
+            echo "No tags found for previous version $PREV_VERSION"
+            exit 1
+          fi
+
+          echo "HIGHEST_TAG=$HIGHEST_TAG"
+          PREVIOUS_RELEASE_COMMIT=$(git rev-list -n 1 $HIGHEST_TAG)
+          echo "PREVIOUS_RELEASE_COMMIT=$PREVIOUS_RELEASE_COMMIT"
+          echo "PREVIOUS_RELEASE_COMMIT=$PREVIOUS_RELEASE_COMMIT" >> $GITHUB_ENV
+
+      # If we're on a release branch we need to download the previous release binaries
+      - name: Download latest release binaries for release branch.
+        if: env.IS_RELEASE_BRANCH == 'true'
         uses: dawidd6/action-download-artifact@e7466d1a7587ed14867642c2ca74b5bcc1e19a2d
         with:
           workflow: release-berghain.yml
           name: chainflip-backend-bin
+          commit: ${{ env.PREVIOUS_RELEASE_COMMIT }}
+          github_token: ${{ secrets.CF_BACKEND_GITHUB_TOKEN }}
+          path: latest-release
+
+      # If we're on main then the latest run of the release-sisyphos.yml workflow will have the latest release binaries
+      # Therefore we don't need to provide a commit.
+      - name: Download latest release binaries for main/PR branches.
+        if: env.IS_RELEASE_BRANCH == 'false'
+        uses: dawidd6/action-download-artifact@e7466d1a7587ed14867642c2ca74b5bcc1e19a2d
+        with:
+          workflow: release-sisyphos.yml
+          name: chainflip-backend-bin
           github_token: ${{ secrets.CF_BACKEND_GITHUB_TOKEN }}
           path: latest-release