chore change license things

api.go

api_test.go

benchmark_test.go

change.go

change_test.go

constants.go

doc.go

env.go

env_test.go

error.go

error_test.go

export.go

export_test.go

file.go

file_test.go

filesystem.go

filesystem_test.go

flags.go

flags_test.go

format.go