make change to update_generation_config.sh

.github/scripts/hermetic_library_generation.sh

@@ -75,16 +75,8 @@ workspace_name="/workspace"
 baseline_generation_config="baseline_generation_config.yaml"
 message="chore: generate libraries at $(date)"
 
-# there's no local branch when running in GitHub action,
-# thus no need to use `git pull`.
 git checkout "${target_branch}"
 git checkout "${current_branch}"
-# only allow fast-forward merging; exit with non-zero result if there's merging
-# conflict.
-if git merge -m "chore: merge ${target_branch} into ${current_branch}" "${target_branch}" -ne 0; then
-  echo "Merge ${target_branch} into ${current_branch} has conflict, exit."
-  exit 1
-fi
 
 # copy generation configuration from target branch to current branch.
 git show "${target_branch}":"${generation_config}" > "${baseline_generation_config}"

.github/scripts/update_googleapis_commit.sh

@@ -64,6 +64,13 @@ else
   gh pr checkout "${pr_num}"
 fi
 
+# only allow fast-forward merging; exit with non-zero result if there's merging
+# conflict.
+if git merge -m "chore: merge ${base_branch} into ${current_branch}" "${base_branch}" -ne 0; then
+  echo "Merge ${base_branch} into ${current_branch} has conflict, exit."
+  exit 1
+fi
+
 mkdir tmp-googleapis
 # use partial clone because only commit history is needed.
 git clone --filter=blob:none https://github.com/googleapis/googleapis.git tmp-googleapis

hermetic_build/library_generation/owlbot/templates/java_library/.github/scripts/update_generation_config.sh

@@ -105,6 +105,13 @@ else
   gh pr checkout "${pr_num}"
 fi
 
+# Only allow fast-forward merging; exit with non-zero result if there's merging
+# conflict.
+if git merge -m "chore: merge ${base_branch} into ${current_branch}" "${base_branch}" -ne 0; then
+  echo "Merge ${base_branch} into ${current_branch} has conflict, exit."
+  exit 1
+fi
+
 mkdir tmp-googleapis
 # Use partial clone because only commit history is needed.
 git clone --filter=blob:none https://github.com/googleapis/googleapis.git tmp-googleapis