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

[Jeff King <peff@peff.net>]

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;
 }
 

-Peff