test-reach: add rev-list tests
The rev-list command is critical to Git's functionality. Ensure it
works in the three commit-graph environments constructed in
t6600-test-reach.sh. Here are a few important types of rev-list
operations:
* Basic: git rev-list --topo-order HEAD
* Range: git rev-list --topo-order compare..HEAD
* Ancestry: git rev-list --topo-order --ancestry-path compare..HEAD
* Symmetric Difference: git rev-list --topo-order compare...HEAD
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>