Subject: Re: [PATCH v3 1/2] diff --no-index: optionally follow symlinks

From: Dennis Kaarsemaker <[email-masked]>
Date: Mon, 20 Mar 2017 11:50:35 +0100

On Sun, 2017-03-19 at 15:14 -0700, Junio C Hamano wrote:
> Dennis Kaarsemaker <[email-masked]> writes:
> 
> > diff --git a/diff.c b/diff.c
> > index be11e4ef2b..2afecfb939 100644
> > --- a/diff.c
> > +++ b/diff.c
> > @@ -2815,7 +2815,7 @@ int diff_populate_filespec(struct diff_filespec *s, unsigned int flags)
> >  		s->size = xsize_t(st.st_size);
> >  		if (!s->size)
> >  			goto empty;
> > -		if (S_ISLNK(st.st_mode)) {
> > +		if (S_ISLNK(s->mode)) {
> >  			struct strbuf sb = STRBUF_INIT;
> >  
> >  			if (strbuf_readlink(&sb, s->path, s->size))
> > @@ -2825,6 +2825,10 @@ int diff_populate_filespec(struct diff_filespec *s, unsigned int flags)
> >  			s->should_free = 1;
> >  			return 0;
> >  		}
> > +		if (S_ISLNK(st.st_mode)) {
> > +			stat(s->path, &st);
> > +			s->size = xsize_t(st.st_size);
> 
> Doesn't this affect --no-index mode?  We never need to do a wasteful
> stat() after lstat() and we are penalizing the normal codepath with
> this change, no?

the S_ISLNK(s->mode) conditional above is for the normal codepath,
which returns early. So the stat I added is only done for symlinks in
no_index mode.

> > @@ -3884,7 +3888,11 @@ int diff_opt_parse(struct diff_options *options,
> >  	else if (!strcmp(arg, "--no-follow")) {
> >  		DIFF_OPT_CLR(options, FOLLOW_RENAMES);
> >  		DIFF_OPT_CLR(options, DEFAULT_FOLLOW_RENAMES);
> > -	} else if (!strcmp(arg, "--color"))
> > +	} else if (!strcmp(arg, "--dereference"))
> > +		DIFF_OPT_SET(options, DEREFERENCE);
> > +	else if (!strcmp(arg, "--no-dereference"))
> > +		DIFF_OPT_CLR(options, DEREFERENCE);
> > +	else if (!strcmp(arg, "--color"))
> >  		options->use_color = 1;
> 
> Also shouldn't be some code to detect --[no-]dereference options
> given when --no-index is not in effect and error out?  As the patch
> title says, this change should be a no-op for normal codepath and
> only affect the no-index hack.

But erroring out isn't a no-op. With the current patch you can do 
--dereference without --no-index and it simply wouldn't affect
anything. 

I don't mind either way, so I'll make it error out.
-- 
Dennis Kaarsemaker
http://www.kaarsemaker.net