pwd prints /tmp/... style paths, not C:\... needed for $TESTTMP to be
substituted.
In the final test, for whatever reason, Windows was missing EOL in the files and
printing:
[wdir] changedlines: printf: warning: ignoring excess arguments, starting with 'printf'
even though it was trying to run:
printf "Line ranges:\n"; printf "2 through 2\n";
I tried wrapping both :command and :linerange in sh -c "...", and while that
fixed the missing EOL, it missed the "2 through 2" output.