Add SKIP_FULL_HISTORY to skip fetch the entire git history

For monorepos fetch the entire history can take excessively long. If no automations are used that use git history, this can be skipped now.

Author: vlussenburg

action.yml

@@ -52,6 +52,7 @@ runs:
         ref: ${{ inputs.base_ref }}
         path: gitstream/repo/
         token: ${{ fromJSON(fromJSON(inputs.client_payload)).githubToken || github.token }}
+        fetch-depth: 1
 
     - name: Escape single quotes
       id: safe-strings
@@ -125,16 +126,21 @@ runs:
         ARTIFACT_OUTCOME_CM_REPO_ARG: ${{ steps.download-cache-for-cm-repo.outcome }}
       with:
         script: require('${{ github.action_path }}/scripts/check-cache-download-status')(core);
-
+    
     - name: Checkout Pull Request branches history
       if: ${{ env.SHOULD_CHECKOUT == 'true' }}
       shell: bash
+      env:
+        # Use 1 for shallow fetch when SKIP_FULL_HISTORY is non‐empty,
+        # otherwise default to 2147483647 for effectively unlimited 
+        DEPTH: ${{ env.SKIP_FULL_HISTORY && 1 || 2147483647 }}
       run: |
-        ALL=2147483647
-        cd gitstream && cd repo
-        git fetch --deepen=$ALL origin $'${{ steps.safe-strings.outputs.base_ref }}'
+        cd gitstream/repo
+
+        # both origin and upstream use the same DEPTH
+        git fetch --deepen=$DEPTH origin $'${{ steps.safe-strings.outputs.base_ref }}'
         git remote add upstream $'${{ steps.safe-strings.outputs.url }}'
-        git fetch --deepen=$ALL upstream $'${{ steps.safe-strings.outputs.head_ref }}'
+        git fetch --deepen=$DEPTH upstream $'${{ steps.safe-strings.outputs.head_ref }}'
         git checkout -b $'upstream/${{ steps.safe-strings.outputs.head_ref}}' $'upstream/${{ steps.safe-strings.outputs.head_ref}}'
         git checkout $'${{ steps.safe-strings.outputs.base_ref }}'
         git checkout $'${{ steps.safe-strings.outputs.head_ref }}'