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

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

[Matthew Booth]

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>
=========

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:

https://stackoverflow.com/questions/31709785/git-line-log-git-l-suppress-diff

Matt
-- 
Matthew Booth
Red Hat OpenStack Engineer, Compute DFG

Phone: +442070094448 (UK)

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

[Jeff King]

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

[PATCH] line-log: suppress diff output with "-s"

[Jeff King]

On Mon, Feb 25, 2019 at 12:18:17PM -0500, Jeff King wrote:

> > 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?

Here it is with a test and a commit message (I don't think any doc
update is necessary; as you noted, the docs already imply this is what
should happen).

-- >8 --
Subject: [PATCH] line-log: suppress diff output with "-s"

When "-L" is in use, we ignore any diff output format that the user
provides to us, and just always print a patch (with extra context lines
covering the whole area of interest). It's not entirely clear what we
should do with all formats (e.g., should "--stat" show just the diffstat
of the touched lines, or the stat for the whole file?).

But "-s" is pretty clear: the user probably wants to see just the
commits that touched those lines, without any diff at all. Let's at
least make that work.

Signed-off-by: Jeff King <peff@peff.net>
---
This punts completely on the larger question of what should happen with
other formats like "--stat", "--raw", etc. They'll continue to be
ignored entirely and we'll generate the line-log patch. Possibly we
should detect and complain?

 line-log.c          | 3 ++-
 t/t4211-line-log.sh | 7 +++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/line-log.c b/line-log.c
index 24e21731c4..863f5cbe0f 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;
 }
 
diff --git a/t/t4211-line-log.sh b/t/t4211-line-log.sh
index bd5fe4d148..c9f2036f68 100755
--- a/t/t4211-line-log.sh
+++ b/t/t4211-line-log.sh
@@ -115,4 +115,11 @@ test_expect_success 'range_set_union' '
 	git log $(for x in $(test_seq 200); do echo -L $((2*x)),+1:c.c; done)
 '
 
+test_expect_success '-s shows only line-log commits' '
+	git log --format="commit %s" -L1,24:b.c >expect.raw &&
+	grep ^commit expect.raw >expect &&
+	git log --format="commit %s" -L1,24:b.c -s >actual &&
+	test_cmp expect actual
+'
+
 test_done
-- 
2.21.0.672.g12e864cee7

Re: [PATCH] line-log: suppress diff output with "-s"

[SZEDER Gábor]

On Mon, Feb 25, 2019 at 12:32:49PM -0500, Jeff King wrote:
> diff --git a/line-log.c b/line-log.c
> index 24e21731c4..863f5cbe0f 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);

Note that the result of this lookup_line_range() call is only used
when we do show the diff below; if we don't, there is no use calling
it.

>  	show_log(rev);
> -	dump_diff_hacky(rev, range);
> +	if (!(rev->diffopt.output_format & DIFF_FORMAT_NO_OUTPUT))
> +		dump_diff_hacky(rev, range);
>  	return 1;
>  }
>  

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

[Randall S. Becker]

On February 25, 2019 12:18, Jeff King wrote:
> To: Matthew Booth <mbooth@redhat.com>
> Cc: git@vger.kernel.org
> 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.

Re: [PATCH] line-log: suppress diff output with "-s"

[Jeff King]

On Mon, Feb 25, 2019 at 06:59:18PM +0100, SZEDER Gábor wrote:

> On Mon, Feb 25, 2019 at 12:32:49PM -0500, Jeff King wrote:
> > diff --git a/line-log.c b/line-log.c
> > index 24e21731c4..863f5cbe0f 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);
> 
> Note that the result of this lookup_line_range() call is only used
> when we do show the diff below; if we don't, there is no use calling
> it.

Thanks. I think sometimes we can depend on an optimizing compiler to
delay the initialization until use, but in this case the function call
is much too complex to be reordered. Here's a v2 which bumps it down.

-- >8 --
Subject: [PATCH v2] line-log: suppress diff output with "-s"

When "-L" is in use, we ignore any diff output format that the user
provides to us, and just always print a patch (with extra context lines
covering the whole area of interest). It's not entirely clear what we
should do with all formats (e.g., should "--stat" show just the diffstat
of the touched lines, or the stat for the whole file?).

But "-s" is pretty clear: the user probably wants to see just the
commits that touched those lines, without any diff at all. Let's at
least make that work.

Signed-off-by: Jeff King <peff@peff.net>
---
 line-log.c          | 6 ++++--
 t/t4211-line-log.sh | 7 +++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/line-log.c b/line-log.c
index 24e21731c4..59248e37cc 100644
--- a/line-log.c
+++ b/line-log.c
@@ -1103,10 +1103,12 @@ static int process_all_files(struct line_log_data **range_out,
 
 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)) {
+		struct line_log_data *range = lookup_line_range(rev, commit);
+		dump_diff_hacky(rev, range);
+	}
 	return 1;
 }
 
diff --git a/t/t4211-line-log.sh b/t/t4211-line-log.sh
index bd5fe4d148..c9f2036f68 100755
--- a/t/t4211-line-log.sh
+++ b/t/t4211-line-log.sh
@@ -115,4 +115,11 @@ test_expect_success 'range_set_union' '
 	git log $(for x in $(test_seq 200); do echo -L $((2*x)),+1:c.c; done)
 '
 
+test_expect_success '-s shows only line-log commits' '
+	git log --format="commit %s" -L1,24:b.c >expect.raw &&
+	grep ^commit expect.raw >expect &&
+	git log --format="commit %s" -L1,24:b.c -s >actual &&
+	test_cmp expect actual
+'
+
 test_done
-- 
2.21.0.674.ga8a7ac9a24