Merge branch 'ps/maintenance-missing-tasks'

Make repository clean-up tasks "gc" can do available to "git maintenance" front-end. * ps/maintenance-missing-tasks: builtin/maintenance: introduce "rerere-gc" task builtin/gc: move rerere garbage collection into separate function builtin/maintenance: introduce "worktree-prune" task builtin/gc: move pruning of worktrees into a separate function builtin/gc: remove global variables where it is trivial to do builtin/gc: fix indentation of `cmd_gc()` parameters