On Tue, 30 Jan 2018 16:39:30 -0500
Derrick Stolee [off-list ref] wrote:

+  Commit Data (ID: {'C', 'G', 'E', 'T' }) (N * (H + 16) bytes)
+    * The first H bytes are for the OID of the root tree.
+    * The next 8 bytes are for the int-ids of the first two parents
+      of the ith commit. Stores value 0xffffffff if no parent in that
+      position. If there are more than two parents, the second value
+      has its most-significant bit on and the other bits store an array
+      position into the Large Edge List chunk.

[snip]

+  Large Edge List (ID: {'E', 'D', 'G', 'E'})
+      This list of 4-byte values store the second through nth parents for
+      all octopus merges. The second parent value in the commit data is a
+      negative number pointing into this list. 

Looking at the paragraph which I quoted before the [snip], this sentence
is confusing (in particular, the second parent value is not interpreted
as the normal two's-complement negative value, and the semantics of
negative values indexing into the list is unclear). Maybe it's better to
omit it entirely.