chore: add workflow to move the major version tag (#2)

Related to https://github.com/tweag/scalable-builds-group/issues/138.

Author: cgrindel

.github/workflows/move_major_ver_tag_on_release.yml

@@ -0,0 +1,43 @@
+name: Move Major Version Tag on Release
+
+on:
+  release:
+    types: [ published ]
+  workflow_dispatch:
+    inputs:
+      release_tag:
+        required: true
+        type: string
+
+jobs:
+  move_major_version_tag:
+    runs-on: ubuntu-latest
+    steps:
+
+      # Checks out the code from your repository with all history for all 
+      # branches and tags. This is important if the workflow is launched via
+      # workspace_dispatch event. It ensures that we can find the release tag
+      # and the major version tag.
+      - uses: actions/checkout@v4
+        with:
+          # Fetch all history for all branches and tags
+          fetch-depth: 0
+
+      # Configures the git user config. This is necessary when making changes
+      # to a git repository.
+      - uses: cgrindel/gha_configure_git_user@v1
+
+      # The release tag can come into the workflow via the release event or as
+      # a workflow_dispatch event. This step finds the first non-empty value
+      # and outputs it as `selected_value`.
+      - name: Resolve release_tag
+        id: resolve_release_tag
+        uses: cgrindel/gha_select_value@v1
+        with: 
+          value0: ${{ github.event.release.tag_name }}
+          value1: ${{ github.event.inputs.release_tag }}
+
+      # Create or move the major version tag
+      - uses: cgrindel/gha_move_major_version_tag@v1
+        with:
+          release_tag: ${{ steps.resolve_release_tag.outputs.selected_value }}