runtests: restore `-k` option and actively process as no-op

Restore processing this option to avoid falling it through and
misinterpreted as something else, which in turn disables tests.

Exit with an error instead. We delete completely in December 2026.

Reported-by: Sam James
Bug: https://github.com/curl/curl/pull/22100#issuecomment-4789828929
Follow-up to 04305a3e40989d3731e97bd0ef41bbd55c680a3f #22100
Follow-up to 6617db6a7ed322d28322896aa20bcabf3a479e7c #4035

Closes #22157

diff --git a/tests/runtests.pl b/tests/runtests.pl
index 61949614b970eae116d392a85036184e58535db8..a326fc37b69ef6a065e08fa2eabf09a49d83042f 100755 (executable)
--- a/tests/runtests.pl
+++ b/tests/runtests.pl
@@ -2539,6 +2539,10 @@ while(@ARGV) {
             $jobs = $1;
         }
     }
+    elsif($ARGV[0] eq "-k") {  # delete this check after December 2026
+        print "Option -k became always-on in 7.65.2 (2019) and now a no-op. Delete it to continue.\n";
+        exit;
+    }
     elsif($ARGV[0] eq "-r") {
         # run time statistics needs Time::HiRes
         if($Time::HiRes::VERSION) {