Silly little tool for making parallel_schedule variants

I got tired of wondering what timing dependencies might still be lurking
in the parallel regression tests, and wrote a little Perl script to find
out by making variant versions of the parallel_schedule file.

Essentially, the script forces each test in a parallel group to run
before all the other ones in its group, and also after all the other
ones. This isn't a completely bulletproof check: you could imagine
that test A might be unhappy about some intermediate state created by
test B, while not being unhappy with either the starting or ending
states. But it's a lot better than guess-and-hope.

The script successfully exposed the problem reported earlier today by
Robert Hentosh (create_index test depends on create_misc having run),
and didn't find any other problems, which I guess is a good sign.
(I've now committed a fix for that mistake, BTW.)

I'm not sure if the script has any long-term usefulness (anyone feel it
deserves to get into CVS in src/tools/?). But I'll attach it anyway
just so it gets into the pghackers archives.

To use it you'd do something like

mkdir scheds
./sched_variants parallel_schedule scheds/sch
for f in scheds/sch*
do
echo $f
/bin/sh ./pg_regress --schedule=$f
ff=`basename $f`
mv regression.out scheds/regression.out.$ff
mv regression.diffs scheds/regression.diffs.$ff
done

regards, tom lane