Re: pg_regress: schedule multi-line test groups

Hello

This looks like a good feature, but I think the parser needs some improvements:

1. A test name directly followed by # is silently dropped

test: a b#note

or

test:
a
b# depends on a

Will only run 'a'

2. An empty or comment-only schedule file now fails

3. The --max-concurrent-tests error reports the wrong line

test:
a
b
c
d
test: a

With --max-concurrent-tests=3 this reports "line 6: test: a". With a
trailing comment after the group it reports the comment line instead.
Maybe it should point to the start of the test?

4. (2) and (3) both come from the goto structure. Wouldn't a
run_test_group() helper be simpler?

5.

EFFECTIVE CONCURRENCY
=====================
This also add for each group a note about the average execution
concurrency achieved during the test.

# parallel group (2 tests): brin_bloom brin_multi
# effective concurrency 1.46 / 2

Wouldn't it be better to separate this part into a separate patch file?