podcheck.t: Send helpful error output to stderr

While we do try to keep stderr clean for tests, that is for *passing*
tests.  If the diagnostic output goes to stdout instead, then nobody
gets to see it for ‘make test’, which means that the script has to
be re-run by itself just to find out what failed.  Since this is a
long-running test, that is quite inconvenient.

Also mention which .t the output is coming from.

1 files changed, 12 insertions, 8 deletions

diff --git a/t/porting/podcheck.t b/t/porting/podcheck.t
index f0c3990951..a6c8528865 100644
--- a/t/porting/podcheck.t
+++ b/t/porting/podcheck.t
@@ -531,16 +531,20 @@ sub suppressed {
         last SKIP;
     }
 
-    sub note {
-        my $message = shift;
+    sub _note {
+        my ($andle, $message) = @_;
 
         chomp $message;
 
-        print $message =~ s/^/# /mgr;
-        print "\n";
+        print $andle $message =~ s/^/# /mgr;
+        print $andle "\n";
         return;
     }
 
+    sub note { unshift @_, \*STDOUT; goto &_note }
+
+    sub diag { unshift @_, \*STDERR; goto &_note }
+
     END {
         if ($planned && $planned != $current_test) {
             print STDERR
@@ -2133,7 +2137,7 @@ foreach my $filename (@files) {
         }
         ok(@diagnostics == $thankful_diagnostics, $output);
         if (@diagnostics) {
-            note(join "", @diagnostics,
+            diag(join "", @diagnostics,
             "See end of this test output for your options on silencing this");
         }
 
@@ -2165,7 +2169,7 @@ if (%files_with_unknown_issues) {
                         : "were $were_count_files files";
     my $message = <<EOF;
 
-HOW TO GET THIS .t TO PASS
+HOW TO GET ${\__FILE__} TO PASS
 
 There $were_count_files that had new potential problems identified.
 Some of them may be real, and some of them may be false positives because
@@ -2204,9 +2208,9 @@ EOF
    and change the count of known potential problems to -1.
 EOF
 
-    note($message);
+    diag($message);
 } elsif (%files_with_fixes) {
-    note(<<EOF
+    diag(<<EOF
 To teach this test script that the potential problems have been fixed,
 $how_to
 EOF