bisect run: fix the error message

In d1bbbe4 (bisect--helper: reimplement `bisect_run` shell function
in C, 2021-09-13), we ported the `bisect run` subcommand to C, including
the part that prints out an error message when the implicit `git bisect
bad` or `git bisect good` failed.

However, the error message was supposed to print out whether the state
was "good" or "bad", but used a bogus (because non-populated) `args`
variable for it. This was fixed in [1], but as of [2] (when
`bisect--helper` was changed to the present `bisect-state') the error
message still talks about implementation details that should not
concern end users.

Fix that, and add a regression test to ensure that the intended form of
the error message.

1. 80c2e96 (bisect--helper: report actual bisect_state() argument
   on error, 2022-01-18
2. f37d0bd (bisect: fix output regressions in v2.30.0, 2022-11-10)

Helped-by: Elijah Newren <[email protected]>
Signed-off-by: Johannes Schindelin <[email protected]>
Signed-off-by: Ævar Arnfjörð Bjarmason <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: dscho

builtin/bisect.c

@@ -1292,7 +1292,7 @@ static int bisect_run(struct bisect_terms *terms, int argc, const char **argv)
 			puts(_("bisect found first bad commit"));
 			res = BISECT_OK;
 		} else if (res) {
-			error(_("bisect run failed: 'bisect-state %s'"
+			error(_("bisect run failed: 'git bisect %s'"
 				" exited with error code %d"), new_state, res);
 		} else {
 			continue;

t/t6030-bisect-porcelain.sh

@@ -1221,4 +1221,14 @@ test_expect_success 'bisect state output with bad commit' '
 	grep -F "waiting for good commit(s), bad commit known" output
 '
 
+test_expect_success 'verify correct error message' '
+	git bisect reset &&
+	git bisect start $HASH4 $HASH1 &&
+	write_script test_script.sh <<-\EOF &&
+	rm .git/BISECT*
+	EOF
+	test_must_fail git bisect run ./test_script.sh 2>error &&
+	grep "git bisect good.*exited with error code" error
+'
+
 test_done