Allow PatchListLoader to use recursive merger

The automerge "base" created on merge commits should use the
recursive merger, if it has not been disabled on this server.

Switching to recursive allows handling changes that require
the virtual common ancestor to be built when multiple merge
bases are discovered for the two parents.

Change-Id: Ica2daa6bd0a38f7fa1430bed28bd7f54d3bfb2c4
3 files changed