On Wed, Mar 20, 2019 at 10:49:55PM +0000, Thomas Gummerer wrote:
> In the scripted 'git stash show' when no arguments are passed, we just
> pass '--stat' to 'git diff'. When any argument is passed to 'stash
> show', we no longer pass '--stat' to 'git diff', and pass whatever
> flags are passed directly through to 'git diff'.
>
> By default 'git diff' shows the patch output. So when we a user uses
> 'git stash show --patience', they would be shown the diff as expected,
> using the patience algorithm. '--patience' in this case only changes
> the diff algorithm, but does not cause 'git diff' to show the diff by
> itself. The diff is shown because that's the default behaviour of
> 'git diff'.
>
> In the C version of 'git stash show', we try to emulate that behaviour
> using the internal diff API. However we forgot to set up the default
> output format, in case it wasn't set by any of the flags that were
> passed through. So 'git stash show --patience' in the builtin version
> of stash would be completely silent, while it would show the diff in
> the scripted version.
>
> The same thing would happen for other flags that only affect the way a
> patch is displayed, rather than switching to a different output format
> than the default one.
>
> Fix this by setting up the default output format for 'git diff'.
>
> Reported-by: Denton Liu <liu.denton@xxxxxxxxx>
> Signed-off-by: Thomas Gummerer <t.gummerer@xxxxxxxxx>
> ---
>
> Thanks Peff and Junio for your comments on the previous round.
>
> Compared to v1, this uses the --patience flags for the tests now, and
> mentions only the --patience flag in the commit message. While the
> original report was about -v, I do agree that --patience is more
> relevant here.
>
> I think this also deserves some explanation of what didn't change,
> especially after what I said in [*1*]. We're still not using the
> 'diff_opt_parse()' option parser, as it doesn't understand '-v' for
> example. 'setup_revisions()' understands that, but 'diff_opt_parse()'
> doesn't, so we'd still have a change in behaviour at least there.
> After discovering that I gave up on that approach.
>
> The other thing that was pointed out is the 'diff_setup_done()' call
> here. 'diff_setup_done()' is already called inside of
> 'setup_revisions()', so we don't need to do it again, unless we change
> the output format, which is what we are doing here. In fact this is
> the same way it's implemented in 'builtin/diff.c'.
>
> *1*: <20190320214504.GC32487@xxxxxxxxxxxxxxxxxxxxxxxx>
>
> builtin/stash.c | 4 ++++
> t/t3903-stash.sh | 18 ++++++++++++++++++
> 2 files changed, 22 insertions(+)
>
> diff --git a/builtin/stash.c b/builtin/stash.c
> index 51df092633..012662ce68 100644
> --- a/builtin/stash.c
> +++ b/builtin/stash.c
> @@ -761,6 +761,10 @@ static int show_stash(int argc, const char **argv, const char *prefix)
> free_stash_info(&info);
> usage_with_options(git_stash_show_usage, options);
> }
> + if (!rev.diffopt.output_format) {
> + rev.diffopt.output_format = DIFF_FORMAT_PATCH;
> + diff_setup_done(&rev.diffopt);
> + }
>
> rev.diffopt.flags.recursive = 1;
> setup_diff_pager(&rev.diffopt);
> diff --git a/t/t3903-stash.sh b/t/t3903-stash.sh
> index 97cc71fbaf..83926ab55b 100755
> --- a/t/t3903-stash.sh
> +++ b/t/t3903-stash.sh
> @@ -612,6 +612,24 @@ test_expect_success 'stash show -p - no stashes on stack, stash-like argument' '
> test_cmp expected actual
> '
>
> +test_expect_success 'stash show -v shows diff' '
s/-v/--patience/
Missed this in my last email, my bad!
> + git reset --hard &&
> + echo foo >>file &&
> + STASH_ID=$(git stash create) &&
> + git reset --hard &&
> + cat >expected <<-EOF &&
> + diff --git a/file b/file
> + index 7601807..71b52c4 100644
> + --- a/file
> + +++ b/file
> + @@ -1 +1,2 @@
> + baz
> + +foo
> + EOF
> + git stash show --patience ${STASH_ID} >actual &&
> + test_cmp expected actual
> +'
> +
> test_expect_success 'drop: fail early if specified stash is not a stash ref' '
> git stash clear &&
> test_when_finished "git reset --hard HEAD && git stash clear" &&
> --
> 2.21.0.226.g764ec437b0.dirty
>
