Re: [PATCH 4/8] sparse-checkout: cone mode does not recognize "**"

> From: Derrick Stolee <dstolee@microsoft.com>
> 
> When core.sparseCheckoutCone is enabled, the 'git sparse-checkout set'
> command creates a restricted set of possible patterns that are used
> by a custom algorithm to quickly match those patterns.
> 
> If a user manually edits the sparse-checkout file, then they could
> create patterns that do not match these expectations. The cone-mode
> matching algorithm can return incorrect results. The solution is to
> detect these incorrect patterns, warn that we do not recognize them,
> and revert to the standard algorithm.
> 
> Check each pattern for the "**" substring, and revert to the old
> logic if seen. While technically a "/<dir>/**" pattern matches
> the meaning of "/<dir>/", it is not one that would be written by
> the sparse-checkout builtin in cone mode. Attempting to accept that
> pattern change complicates the logic and instead we punt and do
> not accept any instance of "**".

> diff --git a/dir.c b/dir.c
> index 22d08e61c2..f8e350dda2 100644
> --- a/dir.c
> +++ b/dir.c
> @@ -651,6 +651,13 @@ static void add_pattern_to_hashsets(struct pattern_list *pl, struct path_pattern
>  		return;
>  	}
>  
> +	if (strstr(given->pattern, "**")) {
> +		/* Not a cone pattern. */
> +		pl->use_cone_patterns = 0;
> +		warning(_("unrecognized pattern: '%s'"), given->pattern);
> +		goto clear_hashmaps;
> +	}