goldens/prefixes.in

preferred prefixes putting 'build_target' before 'branch_name':
build_specs {
  # keep-sorted-test start prefix_order=build_target,branch_name
  build_target: "//foo/baz"
  branch_name: "dev"
  build_target: "//foo/bar"
  branch_name: "prod"
  # keep-sorted-test end
}

Put the specified prefixes at the end:
items = [
  # keep-sorted-test start prefix_order=,FOO,BAR
  FOO,
  DING,
  BAR
  BATS,
  # keep-sorted-test end
]

Put a group of items in the beginning, another group at the end:
// keep-sorted-test start prefix_order=INIT_,,FINAL_
INIT_FOO,
FINAL_FOO,
INIT_BAR,
FINAL_BAR,
DO_STUFF,
DO_MORE_STUFF,
ZAP_THINGS
// keep-sorted-test end

preferred prefixes with comments:
build_specs {
  # keep-sorted-test start prefix_order=build_target,branch_name
  build_target: "//foo/baz"
  # required for development.
  branch_name: "dev"
  # raise the bar!
  build_target: "//foo/bar"
  branch_name: "prod"
  # keep-sorted-test end
}