Simplify create-release-branch workflow (#9954)

* Simplify create-release-branch workflow

* Checkout release branch at tag

* Update name

Author: sarahchen6

.github/chainguard/self.update-system-tests.create-pr.sts.yaml

@@ -1,4 +1,4 @@
-name: Create Release Branch and Pin System-Tests
+name: Create Release Branch
 
 on:
   push:
@@ -15,24 +15,8 @@ jobs:
   create-release-branch:
     runs-on: ubuntu-latest
     permissions:
-      contents: write # Allow pushing the empty release branch
-      id-token: write # Required for OIDC token federation
+      contents: write # Allow pushing the release branch
     steps:
-      - uses: DataDog/dd-octo-sts-action@acaa02eee7e3bb0839e4272dacb37b8f3b58ba80 # v1.0.3
-        id: octo-sts
-        with:
-          scope: DataDog/dd-trace-java
-          policy: self.update-system-tests.create-pr
-
-      - name: Checkout dd-trace-java master branch
-        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # 5.0.0
-        with:
-          ref: master
-
-      - name: Get head SHA of master branch
-        id: get-head-sha
-        run: echo "sha=$(git rev-parse HEAD)" >> $GITHUB_OUTPUT
-
       - name: Determine tag
         id: determine-tag
         run: |
@@ -53,61 +37,25 @@ jobs:
           TAG=${{ steps.determine-tag.outputs.tag }}
           echo "branch=release/${TAG%.0}.x" >> "$GITHUB_OUTPUT"
 
-      # - name: Check if branch already exists
-      #   id: check-branch
-      #   run: |
-      #     BRANCH=${{ steps.define-branch.outputs.branch }}
-      #     if git ls-remote --heads origin "$BRANCH" | grep -q "$BRANCH"; then
-      #       echo "creating_new_branch=false" >> "$GITHUB_OUTPUT"
-      #       echo "Branch $BRANCH already exists - skipping following steps"
-      #     else
-      #       echo "creating_new_branch=true" >> "$GITHUB_OUTPUT"
-      #       echo "Branch $BRANCH does not exist - proceeding with following steps"
-      #     fi
-
-      # - name: Create and push empty release branch
-      #   if: steps.check-branch.outputs.creating_new_branch == 'true'
-      #   run: |
-      #     git checkout -b "${{ steps.define-branch.outputs.branch }}"
-      #     git push -u origin "${{ steps.define-branch.outputs.branch }}"
-
-      - name: Update system-tests references to latest commit SHA on main
-        # if: steps.check-branch.outputs.creating_new_branch == 'true'
-        run: BRANCH=main ./tooling/update_system_test_reference.sh
-
-      - name: Define temp branch name
-        # if: steps.check-branch.outputs.creating_new_branch == 'true'
-        id: define-temp-branch
-        run: echo "temp-branch=ci/pin-system-tests-$(date +'%Y%m%d')" >> $GITHUB_OUTPUT
+      - name: Checkout dd-trace-java at tag
+        uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # 5.0.0
+        with:
+          ref: ${{ steps.determine-tag.outputs.tag }}
 
-      - name: Commit changes
-        # if: steps.check-branch.outputs.creating_new_branch == 'true'
-        id: create-commit
+      - name: Check if branch already exists
+        id: check-branch
         run: |
-          git config user.name "github-actions[bot]"
-          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
-          git commit -m "chore: Pin system-tests for release branch" .github/workflows/run-system-tests.yaml
-          echo "commit=$(git rev-parse HEAD)" >> $GITHUB_OUTPUT
-
-      - name: Push changes to temp branch
-        # if: steps.check-branch.outputs.creating_new_branch == 'true'
-        uses: DataDog/commit-headless@5a0f3876e0fbdd3a86b3e008acf4ec562db59eee # action/v2.0.1
-        with:
-          token: "${{ steps.octo-sts.outputs.token }}"
-          branch: "${{ steps.define-temp-branch.outputs.temp-branch }}"
-          head-sha: "${{ steps.get-head-sha.outputs.sha }}"
-          create-branch: true
-          command: push
-          commits: "${{ steps.create-commit.outputs.commit }}"
+          BRANCH=${{ steps.define-branch.outputs.branch }}
+          if git ls-remote --heads origin "$BRANCH" | grep -q "$BRANCH"; then
+            echo "creating_new_branch=false" >> "$GITHUB_OUTPUT"
+            echo "Branch $BRANCH already exists - skipping creation"
+          else
+            echo "creating_new_branch=true" >> "$GITHUB_OUTPUT"
+            echo "Branch $BRANCH does not exist - creating it now"
+          fi
 
-      - name: Create pull request from temp branch to release branch
-        # if: steps.check-branch.outputs.creating_new_branch == 'true'
-        env:
-          GH_TOKEN: ${{ steps.octo-sts.outputs.token }}
+      - name: Create and push release branch
+        if: steps.check-branch.outputs.creating_new_branch == 'true'
         run: |
-          gh pr create --title "Pin system-tests for ${{ steps.define-branch.outputs.branch }}" \
-            --base "${{ steps.define-branch.outputs.branch }}" \
-            --head "${{ steps.define-temp-branch.outputs.temp-branch }}" \
-            --label "tag: dependencies" \
-            --label "tag: no release notes" \
-            --body "This PR pins the system-tests reference for the release branch."
+          git checkout -b "${{ steps.define-branch.outputs.branch }}"
+          git push -u origin "${{ steps.define-branch.outputs.branch }}"