Subject: RE: [BUG] git log -L ... -s does not suppress diff output

From: "Randall S. Becker" <[email-masked]>
Date: Mon, 25 Feb 2019 13:46:11 -0500

On February 25, 2019 12:18, Jeff King wrote:
> To: Matthew Booth <[email-masked]>
> Cc: [email-masked]
> Subject: Re: [BUG] git log -L ... -s does not suppress diff output
> 
> On Mon, Feb 25, 2019 at 05:03:50PM +0000, Matthew Booth wrote:
> 
> > Example output:
> >
> > =========
> > $ git --version
> > git version 2.20.1
> >
> > $ git log -L 2957,3107:nova/compute/manager.py -s commit
> > 35ce77835bb271bad3c18eaf22146edac3a42ea0
> > <snip>
> >
> > diff --git a/nova/compute/manager.py b/nova/compute/manager.py
> > --- a/nova/compute/manager.py
> > +++ b/nova/compute/manager.py
> > @@ -2937,152 +2921,151 @@
> >      def rebuild_instance(self, context, instance, orig_image_ref, image_ref,
> >                           injected_files, new_pass, orig_sys_metadata,
> > <snip> =========
> 
> At first I wondered why you would want to do this, since the point of -L is to
> walk through that diff. But I suppose you might want to see just the commits,
> without the actual patch, and that's what "-s" ought to do.
> 
> > git log docs suggest it should not do this:
> >
> >        -s, --no-patch
> >            Suppress diff output. Useful for commands like git show
> > that show the patch by default, or to cancel
> >            the effect of --patch.
> >
> > Couldn't find anything in a search of the archives of this mailing
> > list, although that's obviously far from conclusive. Seems to be
> > longstanding, as it was mentioned on StackOverflow back in 2015:
> 
> I think the issue is just that "-L" follows a very different code path than the
> normal diff generator. Perhaps something like this helps?
> 
> diff --git a/line-log.c b/line-log.c
> index 63df51a08f..ed46a3a493 100644
> --- a/line-log.c
> +++ b/line-log.c
> @@ -1106,7 +1106,8 @@ int line_log_print(struct rev_info *rev, struct
> commit *commit)
>  	struct line_log_data *range = lookup_line_range(rev, commit);
> 
>  	show_log(rev);
> -	dump_diff_hacky(rev, range);
> +	if (!(rev->diffopt.output_format & DIFF_FORMAT_NO_OUTPUT))
> +		dump_diff_hacky(rev, range);
>  	return 1;
>  }

I hit this about 6 months ago while trying to show off git to some colleagues - it was on 2.8.5. Sadly I forgot about it. Glad it came back.
Thanks.