I saw there has been some discussion on bug-gnulib about removing "missing" and some of the other "internal" autotools helper scripts from gnulib. That makes sense, but I didn't see a final conclusion to the discussion?
Meanwhile, I have been unable to autoupdate missing from automake to gnulib -- maybe it's just as well -- because there is a trailing space on what is currently line 138, namely the "blank" line between these other two: printf '%s\n' "'$1' is $msg." configure_deps="'configure.ac' or m4 files included by 'configure.ac'" Best, Karl