Subject: Re: [WIP v1 3/4] mv: add advise_to_reapply hint for moving file into cone

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Thu, 31 Mar 2022 12:30:25 +0200

On Thu, Mar 31 2022, Shaoxuan Yuan wrote:

> Originally, the SKIP_WORKTREE bit is not removed when moving an out-of-cone
> file into sparse cone, thus the moved file does not show up in the working tree.
> Hint the user to use "git sparse-checkout reapply" to reapply the sparsity rules
> to the working tree, by which the SKIP_WORKTREE bit is removed.
>
> Signed-off-by: Shaoxuan Yuan <[email-masked]>
> ---
> I offered this solution becasue I'm not sure how to turn a cache_entry's 
> ce_flags back to a non-sparse state. I tried directly set it to 0 like this:
>
> 	ce->ce_flags = 0;
>
> But the behavior after this seems undefined. The file still won't show up
> in the working tree.
>
> And I found that "git sparse-checkout reapply" seems to be a nice fit for the
> job. But I guess if there is a way (there must be but I don't know) to do it
> direcly in the code, that could also be nice.
>
>  builtin/mv.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/builtin/mv.c b/builtin/mv.c
> index 9da9205e01..5f511fb8da 100644
> --- a/builtin/mv.c
> +++ b/builtin/mv.c
> @@ -138,6 +138,7 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
>  {
>  	int i, flags, gitmodules_modified = 0;
>  	int verbose = 0, show_only = 0, force = 0, ignore_errors = 0, ignore_sparse = 0;
> +	int advise_to_reapply = 0;
>  	struct option builtin_mv_options[] = {
>  		OPT__VERBOSE(&verbose, N_("be verbose")),
>  		OPT__DRY_RUN(&show_only, N_("dry run")),
> @@ -383,6 +384,11 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
>  		pos = cache_name_pos(src, strlen(src));
>  		assert(pos >= 0);
>  		rename_cache_entry_at(pos, dst);
> +		if (!advise_to_reapply &&
> +			!path_in_sparse_checkout(src, &the_index) &&
> +			path_in_sparse_checkout(dst, &the_index)) {
> +				advise_to_reapply = 1;
> +			}

More odd indentation, and the braces aren't needed.

>  	}
>  
>  	if (gitmodules_modified)
> @@ -392,6 +398,9 @@ int cmd_mv(int argc, const char **argv, const char *prefix)
>  			       COMMIT_LOCK | SKIP_IF_UNCHANGED))
>  		die(_("Unable to write new index file"));
>  
> +	if (advise_to_reapply)
> +		printf(_("Please use \"git sparse-checkout reapply\" to reapply the sparsity.\n"));
> +

Please see 93026558512 (tracking branches: add advice to ambiguous
refspec error, 2022-03-28) (the OID may change after I send this, as
it's in "seen") for how to add new advise, i.e. we use advise(), add an
enum field, config var etc.