Re: [PATCH 1/5] diff: factor out src/dst prefix setup

> We directly manipulate diffopt's a_prefix and b_prefix to set up either
> the default "a/foo" prefix or the "--no-prefix" variant. Although this
> is only a few lines, it's worth pulling these into their own functions.
> That lets us avoid one repetition already in this patch, but will also
> give us a cleaner interface for callers which want to tweak this
> setting.
> 
> Signed-off-by: Jeff King <peff@peff.net>

> ---
>  diff.c | 19 ++++++++++++++-----
>  diff.h |  2 ++
>  2 files changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/diff.c b/diff.c
> index 469e18aed20..750d1b1a6c3 100644
> --- a/diff.c
> +++ b/diff.c
> @@ -3374,6 +3374,17 @@ void diff_set_mnemonic_prefix(struct diff_options *options, const char *a, const
>  		options->b_prefix = b;
>  }
>  
> +void diff_set_noprefix(struct diff_options *options)
> +{
> +	options->a_prefix = options->b_prefix = "";
> +}
> +
> +void diff_set_default_prefix(struct diff_options *options)
> +{
> +	options->a_prefix = "a/";
> +	options->b_prefix = "b/";
> +}
> +
>  struct userdiff_driver *get_textconv(struct repository *r,
>  				     struct diff_filespec *one)
>  {
> @@ -4674,10 +4685,9 @@ void repo_diff_setup(struct repository *r, struct diff_options *options)
>  		options->flags.ignore_untracked_in_submodules = 1;
>  
>  	if (diff_no_prefix) {
> -		options->a_prefix = options->b_prefix = "";
> +		diff_set_noprefix(options);
>  	} else if (!diff_mnemonic_prefix) {
> -		options->a_prefix = "a/";
> -		options->b_prefix = "b/";
> +		diff_set_default_prefix(options);
>  	}
>  
>  	options->color_moved = diff_color_moved_default;
> @@ -5261,8 +5271,7 @@ static int diff_opt_no_prefix(const struct option *opt,
>  
>  	BUG_ON_OPT_NEG(unset);
>  	BUG_ON_OPT_ARG(optarg);
> -	options->a_prefix = "";
> -	options->b_prefix = "";
> +	diff_set_noprefix(options);
>  	return 0;
>  }
>  
> diff --git a/diff.h b/diff.h
> index 8d770b1d579..2af10bc5851 100644
> --- a/diff.h
> +++ b/diff.h
> @@ -497,6 +497,8 @@ void diff_tree_combined(const struct object_id *oid, const struct oid_array *par
>  void diff_tree_combined_merge(const struct commit *commit, struct rev_info *rev);
>  
>  void diff_set_mnemonic_prefix(struct diff_options *options, const char *a, const char *b);
> +void diff_set_noprefix(struct diff_options *options);
> +void diff_set_default_prefix(struct diff_options *options);
>  
>  int diff_can_quit_early(struct diff_options *);
>