split: add more output to the test
Before this patch, we were not displaying the final graph resulting from the
tests but just the obsolscencence markers. This patch adds more output to the
test to make it more descriptive.
split: fix commit message numbering error in the test
Before this patch, the test was wrong and the successors of a splitted commits
all had the same commit messages. This patch makes the test right making sure
that the numbering of the split successors is accurate.