Draft: streamclone: v3
/notassign_reviewer @mercurial.review
Work on streamclone v3. Solves the following problems:
- reduces the duration of server-side locking (removes the repo scan from the critical section)
- fixes the bug where concurrent pushes make the clone fail (if they split an inline index)
- fixes the bug where corrupted fncache causes clone to succeed and produce corrupted repos