Re: difftool--helper: exit when reading a prompt answer fails

David Aguilar [off-list ref] writes:

quoted

diff --git a/t/t7800-difftool.sh b/t/t7800-difftool.sh
index dc30a51..9cf5dc9 100755
--- a/t/t7800-difftool.sh
+++ b/t/t7800-difftool.sh

@@ -301,6 +301,14 @@ test_expect_success PERL 'say no to the second file' '
 	! grep br2 output
 '
 
+test_expect_success PERL 'ending prompt input with EOF' '
+	git difftool -x cat branch </dev/null >output &&
+	! grep master output &&
+	! grep branch output &&
+	! grep m2 output &&
+	! grep br2 output
+'

Should we use "test_must_fail grep ..." instead of "! grep ..." here?

NO.  We do not expect system-supplied "grep" to dump core and
declare it as a test failure.  test_must_fail is for catching an
expected non-zero status exit from git commands, i.e. when we expect
our binary to correctly notice some condition and report that fact
with non-zero exit status, we do not want to mistake the binary
segfaulting as working correctly.