cabal is a poet

```
cabal-testsuite$ cabal run all -- --help
Error: cabal: The run command is for running a single executable at once. The
target 'all' refers to all the packages in the project which includes the
executable 'cabal', the executable 'setup', the executable 'cabal-tests', the
executable 'hackage-benchmark', the test suite 'unit-tests', the test suite
'rpmvercmp', the test suite 'parser-tests', the test suite 'no-thunks-test',
the test suite 'hackage-tests', the test suite 'custom-setup-tests', the test
suite 'check-tests', the test suite 'cabal-benchmarks', the test suite
'unit-tests', the test suite 'mem-use-tests', the test suite 'long-tests', the
test suite 'integration-tests2', the test suite 'unit-tests' and the test
suite 'unit-tests'.
```
Beautiful!

As much as we should teach our kids to communicate in full sentences, I would like `cabal` to answer me in _tabular_ form:
```
cabal-testsuite$ cabal run all -- --help
Error: cabal: The run command is for running a single executable at once. The
target 'all' refers to all the packages in the project which includes:
- executables: cabal, setup, cabal-tests, hackage-benchmark
- test-suites:
* unit-tests
* rpmvercmp
* parser-tests
* no-thunks-test
* hackage-tests
* custom-tests
* check-tests
* cabal-benchmarks
* mem-use-tests
* long-tests
* integration-tests2
```
(Short lists on one line, long lists one-item-per-line, no duplicates.)
One could also drop the punctuation:
```
- executables: cabal setup cabal-tests hackage-benchmark
- test-suites:
unit-tests
rpmvercmp
parser-tests
no-thunks-test
hackage-tests
custom-tests
check-tests
cabal-benchmarks
mem-use-tests
long-tests
integration-tests2
```
Current pretty-printing frameworks do support separators which end up either horizontal or vertical, depending on the length of the list.