Merge branch 'lf/receive-pack-auto-gc-to-client'

Allow messages that are generated by auto gc during "git push" on the receiving end to be explicitly passed back to the sending end over sideband, so that they are shown with "remote: " prefix to avoid confusing the users. * lf/receive-pack-auto-gc-to-client: receive-pack: send auto-gc output over sideband 2