streamclone: use readexactly when reading stream v2
Yuya Nishihara pointed out that it is safer.
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 4 changes to 4 files
new changesets d326ae2d01ee
updating to branch default
4 files updated, 0 files merged, 0 files removed, 0 files unresolved
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 4 changes to 4 files
new changesets d326ae2d01ee
updating to branch default
4 files updated, 0 files merged, 0 files removed, 0 files unresolved