Merge branch 'rs/ref-fitler-used-atoms-value-fix'

"git branch --sort=..." and "git for-each-ref --format=... --sort=..." did not work as expected with some atoms, which has been corrected. * rs/ref-fitler-used-atoms-value-fix: ref-filter: remove ref_format_clear() ref-filter: move is-base tip to used_atom ref-filter: move ahead-behind bases into used_atom