This updates branch transitions in the composite setup action to use git switch instead of git checkout. The change is scoped to branch selection paths and leaves non-branch checkout behavior unchanged.

• Scope

  • Updated branch fallback logic in .github/actions/setup/action.yml for:
    • submodule branch selection ($MT_BRANCH_NAME → $MT_TARGET_BRANCH_NAME → $MT_DEFAULT_BRANCH_NAME)
    • repository branch selection ($MT_BRANCH_NAME → $MT_TARGET_BRANCH_NAME)

• Behavior preserved

  • SHA-based detached checkout remains unchanged:
    • git -C $REPOSITORY_NAME checkout $MT_SHA

• Representative change

  # before
  git checkout $MT_BRANCH_NAME || git checkout $MT_TARGET_BRANCH_NAME
  
  # after
  git switch $MT_BRANCH_NAME || git switch $MT_TARGET_BRANCH_NAME