Re: [PATCH 2/4] reachable.c: mark reachable objects in index from all worktrees

> Current mark_reachable_objects() only marks objects from index from
> _current_ worktree as reachable instead of all worktrees. Because
> this
> function is used for pruning, there is a chance that objects
> referenced
> by other worktrees may be deleted. Fix that.
> 
> Small behavior change in "one worktree" case, the index is read again
> from file. In the current implementation, if the_index is already
> loaded, the index file will not be read from file again. This adds
> some
> more cost to this operation, hopefully insignificant because
> reachability test is usually very expensive already.
> 
> Reported-by: Johannes Sixt <j6t@kdbg.org>
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
>  reachable.c      | 33 +++++++++++++++++++++++++++++----
>  t/t5304-prune.sh |  9 +++++++++
>  2 files changed, 38 insertions(+), 4 deletions(-)
> 
> diff --git a/reachable.c b/reachable.c
> index 15dbe60..8f67242 100644
> --- a/reachable.c
> +++ b/reachable.c
> @@ -9,6 +9,7 @@
>  #include "cache-tree.h"
>  #include "progress.h"
>  #include "list-objects.h"
> +#include "worktree.h"
>  
>  struct connectivity_progress {
>  	struct progress *progress;
> @@ -155,6 +156,32 @@ int
> add_unseen_recent_objects_to_traversal(struct rev_info *revs,
>  				      FOR_EACH_OBJECT_LOCAL_ONLY);
>  }
>  
> +static void add_objects_from_worktree(struct rev_info *revs)
> +{
> +	struct worktree **worktrees, **p;
> +
> +	worktrees = get_worktrees();
> +	for (p = worktrees; *p; p++) {
> +		struct worktree *wt = *p;
> +		struct index_state istate;
> +
> +		memset(&istate, 0, sizeof(istate));