dagop: just compare with the last value to deduplicate input of revancestors()
Since we're using a max heap, the current rev should be a duplicate only
if it equals to the previous one. We don't have to maintain the whole seen
set.
# reverse(ancestors(tip)) using hg repo
0) 0.086420
1) 0.081051
\{
"node": {node|json},
"changeset_count": {changesets|json},
"changesets": [{join(entries%changelistentry, ", ")}]
}