Re: [PATCH v4] add-patch: response to unknown command

[Junio C Hamano <gitster@pobox.com>]

Eric Sunshine <sunshine@sunshineco.com> writes:

> That's very reminiscent of [1]. Although, unlike [1], the output
> presented to the user in this case is (I suppose) less likely to be
> messed up; only the combined captured output is probably affected. So,
> capturing stdout and stderr separately would indeed be a good idea.

Hmph, something along this line?

It loses to capture how the output should be intermixed, which is
essential to validate what the end-user should see.  As we can see
in the attached patch, we cannot express that "Unknown ..." should
come in between two "Stage addition?" questions, which is a downside.

Between adding fflush() before err() writes, and updating err() to
write to the standard output stream, I am in favor of the latter for
its simplicity (of the mental model of the resulting code, not of
the patch that is required to do so).

diff --git a/t/t3701-add-interactive.sh b/t/t3701-add-interactive.sh
index ed7e414649..a8dfebd8d7 100755
--- a/t/t3701-add-interactive.sh
+++ b/t/t3701-add-interactive.sh
@@ -64,11 +64,12 @@ test_expect_success 'unknown command' '
 	git add -N command &&
 	git diff command >expect &&
 	cat >>expect <<-EOF &&
-	(1/1) Stage addition [y,n,q,a,d,e,p,?]? Unknown command ${SQ}W${SQ} (use ${SQ}?${SQ} for help)
-	(1/1) Stage addition [y,n,q,a,d,e,p,?]?$SP
+	(1/1) Stage addition [y,n,q,a,d,e,p,?]? (1/1) Stage addition [y,n,q,a,d,e,p,?]?$SP
 	EOF
-	git add -p -- command <command >actual 2>&1 &&
-	test_cmp expect actual
+	echo "Unknown command ${SQ}W${SQ} (use ${SQ}?${SQ} for help)" >expect.error &&
+	git add -p -- command <command >actual 2>actual.error &&
+	test_cmp expect actual &&
+	test_cmp expect.error actual.error
 '
 
 test_expect_success 'setup (initial)' '