rev-list --exclude: tests

rev-list --exclude: tests

Add tests for the --exclude=<glob> feature.

A few tests are added for cases where use of globbing and
"--exclude" results in no positive revisions:

 * "--exclude=<glob>" before "--all" etc. resulted in no results;

 * "--stdin" is used but no input was given;

 * "--all" etc. is used but no matching refs are found.

Currently, we fail such a request with the same error message we
would give to a command line that does not specify any positive
revision (e.g. "git rev-list<ENTER>").

We may want to treat these cases differently and not error out, but
the logic to detect that would be common to all of them, so I'd
leave it outside this topic for now, and stop at adding these tests
as food-for-thought.

Signed-off-by: Junio C Hamano <gitster@pobox.com>