update release process to support multiple version

.github/workflows/post-release-mergeback.yml

@@ -1,9 +1,9 @@
-# This workflow runs after a release of the action. It:
-# 1. Merges any changes from the release back into the main branch. Typically, this is just a single
-#    commit that updates the changelog.
-# 2. Tags the merge commit on the release branch that represents the new release with an `v2.x.y`
+# This workflow runs after a merge to any release branch of the action. It:
+# 1. Tags the merge commit on the release branch that represents the new release with n `vN.x.y`
 #    tag
-# 3. Updates the `v2` tag to refer to this merge commit.
+# 2. Updates the `vN` tag to refer to this merge commit.
+# 3. Iff vN == vLatest, merges any changes from the release back into the main branch.
+#    Typically, this is just a single commit that updates the changelog.
 name: Tag release and merge back
 
 on:
@@ -16,7 +16,7 @@ on:
 
   push:
     branches:
-      - releases/v2
+      - releases/v*
 
 jobs:
   merge-back:
@@ -36,6 +36,8 @@ jobs:
         run: echo "${GITHUB_CONTEXT}"
 
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0  # ensure we have all tags and can push commits
       - uses: actions/setup-node@v4
 
       - name: Update git config
@@ -51,6 +53,8 @@ jobs:
           short_sha="${GITHUB_SHA:0:8}"
           NEW_BRANCH="mergeback/${VERSION}-to-${BASE_BRANCH}-${short_sha}"
           echo "newBranch=${NEW_BRANCH}" >> $GITHUB_OUTPUT
+          LATEST_RELEASE_BRANCH=$(git branch -r | grep -E "origin/releases/v[0-9]+$" | sed 's/origin\///g' | sort -V | tail -1 | xargs)
+          echo "latest_release_branch=${LATEST_RELEASE_BRANCH}" >> $GITHUB_OUTPUT
 
       - name: Dump branches
         env:
@@ -59,6 +63,8 @@ jobs:
           echo "BASE_BRANCH ${BASE_BRANCH}"
           echo "HEAD_BRANCH ${HEAD_BRANCH}"
           echo "NEW_BRANCH ${NEW_BRANCH}"
+          echo "LATEST_RELEASE_BRANCH ${LATEST_RELEASE_BRANCH}"
+          echo "GITHUB_REF ${GITHUB_REF}"
 
       - name: Create mergeback branch
         env:
@@ -89,8 +95,6 @@ jobs:
         env:
           VERSION: ${{ steps.getVersion.outputs.version }}
         run: |
-          # Unshallow the repo in order to allow pushes
-          git fetch --unshallow
           # Create the `vx.y.z` tag
           git tag --annotate "${VERSION}" --message "${VERSION}"
           # Update the `vx` tag
@@ -99,13 +103,13 @@ jobs:
           git tag --annotate "${major_version_tag}" --message "${major_version_tag}" --force
           # Push the tags, using:
           # - `--atomic` to make sure we either update both tags or neither (an intermediate state,
-          #   e.g. where we update the v2.x.y tag on the remote but not the v2 tag, could result in
-          #   unwanted Dependabot updates, e.g. from v2 to v2.x.y)
-          # - `--force` since we're overwriting the `vx` tag
+          #   e.g. where we update the vN.x.y tag on the remote but not the vN tag, could result in
+          #   unwanted Dependabot updates, e.g. from vN to vN.x.y)
+          # - `--force` since we're overwriting the `vN` tag
           git push origin --atomic --force refs/tags/"${VERSION}" refs/tags/"${major_version_tag}"
 
       - name: Create mergeback branch
-        if: steps.check.outputs.exists != 'true'
+        if: ${{ steps.check.outputs.exists != 'true' && endsWith(github.ref_name, steps.getVersion.outputs.latest_release_branch) }}
         env:
           VERSION: "${{ steps.getVersion.outputs.version }}"
           NEW_BRANCH: "${{ steps.getVersion.outputs.newBranch }}"