t / t3901-utf8.txton commit run_external_diff: use an argv_array for the environment (ae049c9)
   1: to be sourced in t3901 -- this is utf8
   2GIT_AUTHOR_NAME="Áéí óú" &&
   3GIT_COMMITTER_NAME=$GIT_AUTHOR_NAME &&
   4export GIT_AUTHOR_NAME GIT_COMMITTER_NAME