Merge branch 'jk/ref-filter-error-reporting-fix'

Clean-ups in error messages produced by "git for-each-ref" and friends. * jk/ref-filter-error-reporting-fix: ref-filter: convert email atom parser to use err_bad_arg() ref-filter: truncate atom names in error messages ref-filter: factor out "unrecognized %(foo) arg" errors ref-filter: factor out "%(foo) does not take arguments" errors ref-filter: reject arguments to %(HEAD)