Merge branch 'dt/disable-bitmap-in-auto-gc' into maint

It is natural that "git gc --auto" may not attempt to pack everything into a single pack, and there is no point in warning when the user has configured the system to use the pack bitmap, leading to disabling further "gc". * dt/disable-bitmap-in-auto-gc: repack: die on incremental + write-bitmap-index auto gc: don't write bitmaps for incremental repacks