Draft: Speed up cloning of local forks
Cloning a forked repo on the same shard is slow because the normal Git
transport has to negotiate refs, pack, and unpack objects. This commit
introduces an allow_local
flag, which uses the --local and
--no-hardlinks command-line arguments if the source and target projects
reside on the same storage shard.
Relates to #3377
Edited by Stan Hu