Merge branch 'tb/commit-graph-perm-bits'

Some of the files commit-graph subsystem keeps on disk did not correctly honor the core.sharedRepository settings and some were left read-write. * tb/commit-graph-perm-bits: commit-graph.c: make 'commit-graph-chain's read-only commit-graph.c: ensure graph layers respect core.sharedRepository commit-graph.c: write non-split graphs as read-only lockfile.c: introduce 'hold_lock_file_for_update_mode' tempfile.c: introduce 'create_tempfile_mode'