Projects::RefsController#logs_tree is calling Gitaly n+1 times per request

Gitaly Conversation: gitaly#383 (closed)

Projects::RefsController#logs_tree is calling Gitaly n+1 times per request.

This code needs to be refactored to fetch all required information in a single call.

See https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/13996/diffs#0526d8fcf48a2779ac87de50ed9c7c2c0aefc093_61_54