feat: fix vuln branch setting (#32039)

Author: devindford

.github/workflows/gif_check.yml

@@ -27,8 +27,10 @@ jobs:
     # Branch Name Validation to be run prior to workflow
     - name: Validate branch name and set output
       id: validate
+      env:
+        BRANCH: ${{ github.head_ref }}
       run: |
-        BRANCH="${{ github.head_ref }}"
+        BRANCH="${{ env.BRANCH }}"
         # Allow: letters, numbers, dots, hyphens, underscores, and forward slash
         # This supports the required <name>/<description> format like "user.name/test-this-new-feature"
         if [[ "$BRANCH" =~ ^[a-zA-Z0-9._/-]+$ ]] && [[ ${#BRANCH} -le 200 ]]; then

.github/workflows/preview_link.yml

@@ -33,8 +33,10 @@ jobs:
     # Branch Name Validation to be run prior to workflow
     - name: Validate branch name and set output
       id: validate
+      env:
+        BRANCH: ${{ github.head_ref }}
       run: |
-        BRANCH="${{ github.head_ref }}"
+        BRANCH="${{ env.BRANCH }}"
         # Allow: letters, numbers, dots, hyphens, underscores, and forward slash
         # This supports the required <name>/<description> format like "user.name/test-this-new-feature"
         if [[ "$BRANCH" =~ ^[a-zA-Z0-9._/-]+$ ]] && [[ ${#BRANCH} -le 200 ]] && [[ "$BRANCH" == *"/"* ]]; then

.github/workflows/synthetics.yml

@@ -27,8 +27,10 @@ jobs:
       # Branch Name Validation to be run prior to workflow
       - name: Validate branch name and set output
         id: validate
+        env:
+          BRANCH: ${{ github.event.pull_request.head.ref }}
         run: |
-          BRANCH="${{ github.event.pull_request.head.ref }}"
+          BRANCH="${{ env.BRANCH }}"
           # Allow: letters, numbers, dots, hyphens, underscores, and forward slash
           # This supports the required <name>/<description> format like "user.name/test-this-new-feature"
           if [[ "$BRANCH" =~ ^[a-zA-Z0-9._/-]+$ ]] && [[ ${#BRANCH} -le 200 ]]; then
@@ -42,9 +44,11 @@ jobs:
       - name: Check preview status
         id: check-status
         if: steps.validate.outputs.valid == 'true'
+        env:
+          BRANCH: ${{ steps.validate.outputs.branch }}
         run: |
           # Use the validated branch name from previous step
-          BRANCH="${{ steps.validate.outputs.branch }}"
+          BRANCH="${{ env.BRANCH }}"
           URL="https://docs-staging.datadoghq.com/${BRANCH}"
           SUCCESS_CODES=("200" "302" "304")
           for i in {1..30}