v2t4253-am-keep-cr-dos: avoid using pipes

> Signed-off-by: Boxuan Li <liboxuan@connect.hku.hk>
> ---
> Thanks to Eric Sunshine's review, I've removed spaces after '>'
> and changed 'actual' into 'output'.
> ---
>  t/t4253-am-keep-cr-dos.sh | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/t/t4253-am-keep-cr-dos.sh b/t/t4253-am-keep-cr-dos.sh
> index 553fe3e88e..6e1b73ec3a 100755
> --- a/t/t4253-am-keep-cr-dos.sh
> +++ b/t/t4253-am-keep-cr-dos.sh
> @@ -51,14 +51,16 @@ test_expect_success 'am with dos files without --keep-cr' '
>  
>  test_expect_success 'am with dos files with --keep-cr' '
>  	git checkout -b dosfiles-keep-cr initial &&
> -	git format-patch -k --stdout initial..master | git am --keep-cr -k -3 &&
> +	git format-patch -k --stdout initial..master >output &&
> +	git am --keep-cr -k -3 output &&
>  	git diff --exit-code master
>  '
>  
>  test_expect_success 'am with dos files config am.keepcr' '
>  	git config am.keepcr 1 &&
>  	git checkout -b dosfiles-conf-keepcr initial &&
> -	git format-patch -k --stdout initial..master | git am -k -3 &&
> +	git format-patch -k --stdout initial..master >output &&
> +	git am -k -3 output &&
>  	git diff --exit-code master
>  '

>
> Boxuan Li <liboxuan@connect.hku.hk> writes:
>
> > The exit code of the upstream in a pipe is ignored thus we should avoid
> > using it. By writing out the output of the git command to a file, we can
> > test the exit codes of both the commands.
>
> We are trying to catch breakages in "am" in these two tests (see the
> title of the test file), and we rely on format-patch to correctly
> produce its output---if we assume that the command being tested,
> i.e. "am", could be fed garbage, the tests become pointless.
>
> And once we decide to rely on the correctness of format-patch in
> these two tests, there no longer is a reason to fear that
> invocations of it upstream of a pipe would lose the exit status.
>
> So while the patch is not wrong per-se, but these two changes are
> borderline Meh.
>
> > Signed-off-by: Boxuan Li <liboxuan@connect.hku.hk>
> > ---
> > Thanks to Eric Sunshine's review, I've removed spaces after '>'
> > and changed 'actual' into 'output'.
> > ---
> >  t/t4253-am-keep-cr-dos.sh | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/t/t4253-am-keep-cr-dos.sh b/t/t4253-am-keep-cr-dos.sh
> > index 553fe3e88e..6e1b73ec3a 100755
> > --- a/t/t4253-am-keep-cr-dos.sh
> > +++ b/t/t4253-am-keep-cr-dos.sh
> > @@ -51,14 +51,16 @@ test_expect_success 'am with dos files without --keep-cr' '
> >
> >  test_expect_success 'am with dos files with --keep-cr' '
> >       git checkout -b dosfiles-keep-cr initial &&
> > -     git format-patch -k --stdout initial..master | git am --keep-cr -k -3 &&
> > +     git format-patch -k --stdout initial..master >output &&
> > +     git am --keep-cr -k -3 output &&
> >       git diff --exit-code master
> >  '
> >
> >  test_expect_success 'am with dos files config am.keepcr' '
> >       git config am.keepcr 1 &&
> >       git checkout -b dosfiles-conf-keepcr initial &&
> > -     git format-patch -k --stdout initial..master | git am -k -3 &&
> > +     git format-patch -k --stdout initial..master >output &&
> > +     git am -k -3 output &&
> >       git diff --exit-code master
> >  '

>
> "LI, BO XUAN" <liboxuan@connect.hku.hk> writes:
>
> > Thanks for your review! I can understand your point, but I've got a
> > quick question:
> >
> > What if format-patch really breaks and 'am' magically does not break?
>
> Doesn't that indicate that you are not testing the result of "am"
> adequately?
>
> I am not saying it is *wrong* to split the pipe into two.  I am
> merely saying that it is borderline Meh, as the primary point of
> these two tests are to see how the command downstream of the pipe
> behaves and not the upstream one.