Re: [PATCH v4 3/5] refs: introduce get_worktree_ref_store()

> files-backend at this point is still aware of the per-repo/worktree
> separation in refs, so it can handle a linked worktree.
> 
> Some refs operations are known not working when current files-backend is
> used in a linked worktree (e.g. reflog). Tests will be written when
> refs_* functions start to be called with worktree backend to verify that
> they work as expected.
> 
> Note: accessing a worktree of a submodule remains unaddressed. Perhaps
> after get_worktrees() can access submodule (or rather a new function
> get_submodule_worktrees(), that lists worktrees of a submodule), we can
> update this function to work with submodules as well.
> 
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
>  refs.c | 31 +++++++++++++++++++++++++++++++
>  refs.h |  2 ++
>  2 files changed, 33 insertions(+)
> 
> diff --git a/refs.c b/refs.c
> index 875e30a0b8..a4083caf6a 100644
> --- a/refs.c
> +++ b/refs.c
> @@ -10,6 +10,7 @@
>  #include "object.h"
>  #include "tag.h"
>  #include "submodule.h"
> +#include "worktree.h"
>  
>  /*
>   * List of all available backends
> @@ -1486,6 +1487,9 @@ static struct ref_store *main_ref_store;
>  /* A hashmap of ref_stores, stored by submodule name: */
>  static struct hashmap submodule_ref_stores;
>  
> +/* A hashmap of ref_stores, stored by worktree id: */
> +static struct hashmap worktree_ref_stores;
> +
>  /*
>   * Look up a ref store by name. If that ref_store hasn't been
>   * registered yet, return NULL.
> @@ -1590,6 +1594,33 @@ struct ref_store *get_submodule_ref_store(const char *submodule)
>  	return refs;
>  }
>  
> +struct ref_store *get_worktree_ref_store(const struct worktree *wt)
> +{
> +	struct ref_store *refs;
> +	unsigned int refs_all_capabilities =
> +		REF_STORE_READ | REF_STORE_WRITE |
> +		REF_STORE_ODB | REF_STORE_MAIN;