Merge branch 'tb/commit-graph-object-dir'

The code to compute the commit-graph has been taught to use a more robust way to tell if two object directories refer to the same thing. * tb/commit-graph-object-dir: commit-graph.h: use odb in 'load_commit_graph_one_fd_st' commit-graph.c: remove path normalization, comparison commit-graph.h: store object directory in 'struct commit_graph' commit-graph.h: store an odb in 'struct write_commit_graph_context' t5318: don't pass non-object directory to '--object-dir'