t5333: demonstrate various pseudo-merge bugs

t5333: demonstrate various pseudo-merge bugs

Using the test helper introduced via the previous commit, add various
failing tests demonstrating bugs in the pseudo-merge implementation.

These are all marked as failing with one exception. The "sampleRate=0"
test describes a latent bug, which is only reachable through a code path
that is itself masked by a separate bug. A future commit will fix that
bug, and, in turn, cause the aforementioned test to fail. Accordingly,
that commit will mark the test as failing, and it will be re-marked as
passing in a separate commit which fixes the once-latent bug.

For the rest: the following commits will explain and fix the underlying
bugs in detail.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>