SHIP-0038: Release Branch Workflows

Creating a reusable GitHub Actions workflow to set up release branches
in Shipwright projects, and a corresponding starter workflow template.
These workflows will let Shipwright projects opt into setting up
release branches for project artifacts. The workflows allow branches to
be created at specific git references, allowing release branches to be
set up retroactively.

Signed-off-by: Adam Kaplan <[email protected]>

.github/workflows/release-branch.yml

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+# Reusable release brancher workflow
+# See SHIP-0038: https://github.com/shipwright-io/community/pull/194
+name: Release Brancher
+on:
+  workflow_call:
+    inputs:
+      release-version:
+        required: true
+        type: string
+      git-ref:
+        required: false
+        type: string
+jobs:
+  release-brancher:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        ref: ${{ inputs.git-ref }}
+    - name: Create release branch
+      env:
+        RELEASE_VERSION: release-${{ inputs.release-version }}
+      run: |
+        git switch -c "${RELEASE_VERSION}"
+        git push --set-upstream origin "${RELEASE_VERSION}"

workflow-templates/release-branch.properties.json

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+{
+    "name": "adambkaplan Release Brancher",
+    "description": "Starter workflow for creating release branches",
+    "iconName": "octicon git-branch",
+    "categories": [
+        "Automation"
+    ]
+}

workflow-templates/release-branch.yml

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+# Release branch starter workflow
+# See SHIP-0038: https://github.com/shipwright-io/community/pull/194
+name: Create Release Branch
+on:
+  workflow_dispatch:
+    inputs:
+      release-version:
+        required: true
+        type: string
+        description: "Semantic version for the release branch (vX.Y format)"
+      git-ref:
+        required: false
+        type: string
+        description: "Git ref to create the release branch from (defaults to main)"
+        default: "main"
+jobs:
+  create-release-branch:
+    permissions:
+      contents: write
+    uses: shipwright-io/.github/.github/workflows/release-branch.yml@main
+    with:
+      release-version: ${{ inputs.release-version }}
+      git-ref: ${{ inputs.git-ref }}