Re: [PATCH v2 3/3] diff: Introduce --diff-algorithm command line option

> +--diff-algorithm={patience|minimal|histogram|myers}::
> +	Choose a diff algorithm. The variants are as follows:
> ++
> +--
> +`myers`;;
> +	The basic greedy diff algorithm.
> +`minimal`;;
> +	Spend extra time to make sure the smallest possible diff is
> +	produced.
> +`patience`;;
> +	Use "patience diff" algorithm when generating patches.
> +`histogram`;;
> +	This algorithm extends the patience algorithm to "support
> +	low-occurrence common elements".
> +--
> ++
> +For instance, if you configured diff.algorithm variable to a
> +non-default value and want to use the default one, then you
> +have to use `--diff-algorithm=myers` option.
> +
> +You should prefer this option over the `--minimal`, `--patience` and
> +`--histogram` which are kept just for backwards compatibility.

> diff --git a/diff.c b/diff.c
> index e9a7e4d..3e021d5 100644
> --- a/diff.c
> +++ b/diff.c
> @@ -144,7 +144,7 @@ static int git_config_rename(const char *var, const char *value)
>  	return git_config_bool(var,value) ? DIFF_DETECT_RENAME : 0;
>  }
>  
> -static long parse_algorithm_value(const char *value)
> +long parse_algorithm_value(const char *value)
>  {
>  	if (!value || !strcasecmp(value, "myers"))
>  		return 0;
> @@ -3633,6 +3633,16 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
>  		options->xdl_opts = DIFF_WITH_ALG(options, PATIENCE_DIFF);
>  	else if (!strcmp(arg, "--histogram"))
>  		options->xdl_opts = DIFF_WITH_ALG(options, HISTOGRAM_DIFF);
> +	else if (!prefixcmp(arg, "--diff-algorithm=")) {
> +		long value = parse_algorithm_value(arg+17);
> +		if (value < 0)
> +			return error("option diff-algorithm accepts \"myers\", "
> +				     "\"minimal\", \"patience\" and \"histogram\"");
> +		/* clear out previous settings */
> +		DIFF_XDL_CLR(options, NEED_MINIMAL);
> +		options->xdl_opts &= ~XDF_DIFF_ALGORITHM_MASK;
> +		options->xdl_opts |= value;