When `force` is set to `true` and `start_branch` is set, the
branch will be ovewritten with the new commit based on the
`HEAD` of the `start_branch`.
This commit includes changes to update the `gitaly-proto` gem.
Updates Files::MultiService for the commits API which is in turn used by the
multi-file upload web UI
Ensures that files which should be in LFS are transformed into LFS pointers
Uses Lfs::Transformer which then links LfsObjectProjects on success
When commiting multiple files we're now checking if any of those files
has been modified by another commit and we're rejecting the new commit
in this case.