Optimise merging from a new branch
Optimise merging from a new branch

Previously, we tried to find the LCA between our empty branch and the
branch being merged. Since there was no LCA in the case of a new branch,
this required searching the entire history.

Signed-off-by: Thomas Leonard <ea62ade398c3addd3bcc52285a00e98f3b0c618f@docker.com>

docker/datakit,docker/datakit,docker/datakit