Re: [PATCH] Additional merge-base tests

A Large Angry SCM [off-list ref] writes:

This demonstrates a problem with git-merge-base.
 
+# Setup for second test set
+#
+#   PL  PR
+#  /  \/  \
+# L2  C2  R2
+# |   |   |
+# L1  C1  R1
+# |   |   |
+# L0  C0  R0
+#   \ |  /
+#     S

Cute.

This is a good demonstration that merge-base may not give you
minimal set for pathological cases.  If you want to be through
you could traverse everything to make sure we do not say 'S' is
relevant, but that is quite expensive, so I think there will
always be artifacts of horizon effect like this no matter how
you try to catch it (didn't I keep saying that already?).

However, I do not think it is really a "problem".  At least what
"merge-base --all" did not miss any, that should be OK.

I think the practical way to proceed is to say that the test
condition should really check that we do not _omit_ C2 in the
merge-base --all output.